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1

Control of Surface Attack by Gallium Alloys in Electrical Contacts.  

National Technical Information Service (NTIS)

Electrical contact between a copper plated steel specimen and brushes of graphite and copper through a film of gallium alloy were investigated. Material compatibility phase changes were studied. Techniques of film renewal were tested as were results in in...

R. A. Burton R. G. Burton

1986-01-01

2

Control of Surface Attack by Gallium Alloys. Phase 2.  

National Technical Information Service (NTIS)

The potential for eutectic alloys of Gallium in current collectors is examined. The focus of the program was on GalnSn alloy. Basic properties of the alloy are determined as well as oxide control and corrosion of copper. Designs for high current density c...

R. A. Burton R. G. Burton

1988-01-01

3

Method for Plutonium-Gallium Separation by Anodic Dissolution of a Solid Plutonium-Gallium Alloy  

DOEpatents

Purified plutonium and gallium are efficiently recovered from a solid plutonium-gallium (Pu-Ga) alloy by using an electrorefining process. The solid Pu-Ga alloy is the cell anode, preferably placed in a moving basket within the electrolyte. As the surface of the Pu-Ga anode is depleted in plutonium by the electrotransport of the plutonium to a cathode, the temperature of the electrolyte is sufficient to liquify the surface, preferably at about 500 C, resulting in a liquid anode layer substantially comprised of gallium. The gallium drips from the liquified surface and is collected below the anode within the electrochemical cell. The transported plutonium is collected on the cathode surface and is recovered.

Miller, William E.; Tomczuk, Zygmunt

1998-12-08

4

[Studies on gallium alloys for dental restorations. 2. Electron probe microanalysis for hardened gallium alloys].  

PubMed

Hardened gallium alloys were analyzed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The cores, matrix and white irregular shape phases were visible with SEM. The round or irregular shape cores contained Ag, Pd, Cu and Zn but did not contain Ga and In. The dark irregular shape matrix, which surrounded the core, consisted of Ga-Ag, Ga-Pd, Ga-Cu and Ga-Sn phases. However, the amount of Ga-Sn phase was very low. The white phase in the matrix was Ag-In phase. PMID:2135533

Horibe, T; Okamoto, Y; Miyazaki, K

1990-05-01

5

Machining of iron–gallium alloy for microactuator  

Microsoft Academic Search

We study the micromachining of iron–gallium alloy for use in a microactuator. Iron–gallium (Galfenol) is an iron-based magnetostrictive material with magnetostriction exceeding 200ppm, Young's modulus of 70GPa, and distinctive ductile and machinable properties. An actuator made by small Galfenol component therefore should be simple, robust against external forces and drivable at low voltage. A rod of Galfenol (Fe81.6Ga18.4) prepared by

T. Ueno; E. Summers; T. Higuchi

2007-01-01

6

Gallium arsenic nitride and gallium arsenic bismuth novel optoelectronic alloys  

NASA Astrophysics Data System (ADS)

Forming an alloy from two dissimilar but isovalent semiconductor compounds, A-B and A-C, can form what is called an isoelectronic alloy if two distinctive characteristics are observed: (1) the A-B1-xCx, alloy has a well-defined fundamental band gap as well as other electronic band edges, and (2) at low concentrations (x << 1%) the isovalent impurity C replacing B traps a charge carrier. In this thesis, two GaAs-based isoelectronic alloys are investigated experimentally. The first one, GaAsN, is formed by replacing As by a very small atom attractive to electrons whereas the second, GaAsBi, is formed by replacing As by a very large atom attractive to holes. For GaAsN, the new optical transitions, forbidden in GaAs, originate from the splitting of the quadruply degenerate conduction band at L6c, and become allowed due to the strong perturbation of the potential of N to the band structure of GaAs. The mutual repulsion between the split singlet state and the bottom of the conduction band is the origin of the unusual and non monotonic band gap dependence observed for this alloy. For the first time, a pseudo-donor isoelectronic alloy is identified. First, the band gap energy dependence of GaAsBi on Bi concentration is unusually larger than that observed from other isovalent semiconductor alloys. Similar to the case of GaAsN, this effect results from the strong perturbation caused by Bi on the periodicity of the GaAs regular lattice, lowering the symmetry and redefining the interactions within the band structure. Second, Bi-related excitonic bound states are observed and are likely composed of at least two Bi atoms. The Bi bound state should be located at higher energy, close to the valence band edge or resonant with the valence band. The final aspect relates to the photoluminescence from GaAs doped with a very low N concentration. Using optical spectroscopy with diffraction limited spatial resolution, we have measured the luminescence from single impurity centers formed by two neighboring N atoms in GaAs. Selectively studying individual centers makes it possible to unveil their otherwise concealed polarization anisotropy, analyze their selection rules, identify their particular configuration, map their spatial distribution, and demonstrate the presence of a diversity of local environments.

Francoeur, Sebastien

7

Infrared Absorption in Gallium Phosphide-Gallium Arsenide Alloys I. Absorption in n-type Material  

Microsoft Academic Search

There is an absorption band at 3 ?m in n-type gallium phosphide for which a number of explanations have been advanced. These are discussed, and it is shown that a distinction may be made between them by observing the 3 ?m band as a function of composition in GaPxAs1-x alloys. Experimentally it is found that at liquid nitrogen temperatures the

J W Allen; J W Hodby

1963-01-01

8

Gallium-induced magnesium enrichment on grain boundary and the gallium effect on degradation of tensile properties of aluminum alloys  

Microsoft Academic Search

By applying a controlled amount of gallium (3 mg or 5 mg) to double-notched samples, the effects of the gallium on the grain\\u000a boundary chemistry and tensile properties of AA6061-T4 alloy were investigated. Commercial-purity aluminum AA1050 was used\\u000a for comparison to determine whether alloying elements would correlate with Ga-induced embrittlement and to elucidate the physical\\u000a reason that governed the occurrence

Jun-Yen Uan; Cheng-Chia Chang

2006-01-01

9

Fundamental Studies of the Metallurgical, Electrical, and Optical Properties of Gallium Phosphide and Gallium Phosphide Alloys.  

National Technical Information Service (NTIS)

Abstracts, bibliographic data, oral presentations, and published papers on (1) Diffusion of Sulfur in Gallium Phosphide and Gallium Arsenide, and (2) Properties of Gallium Phosphide Schottky Barrier Rectifiers for Use at High Temperature are presented.

1972-01-01

10

Magnetostrictive bending micro-actuator using iron gallium-alloy  

NASA Astrophysics Data System (ADS)

We investigate a micro bending actuator based on unimorph, lamination of Galfenol (Iron-gallium alloy) and non-magnetic material. Galfenol C-shape yoke bonded with stainless plates (lamination) is wound coils, and is composed close magnetic loop with connected an iron plate. The magnetostriction in longitude direction is constrained by the stainless, thus, the laminations yield bending deformation with the current flowing. The advantage of the actuator is simple, compact and ease of assembling including winding coil, and high tolerance against bending, tensile and impact. We machined the yoke from a plate of 1mm thickness of polycrystalline Galfenol (Fe81.4Ga18.6 Research grade) using ultra high precision cutting technique. The prototype, thickness of 1mm and length of 10mm, was observed the displacement 13?m and 1st resonance at 1.6 kHz, and the high bending (tensile) tolerance withstanding suspended weight of 500g.

Ueno, Toshiyuki; Higuchi, Toshiro

2007-04-01

11

Electron backscatter diffraction of plutonium-gallium alloys  

SciTech Connect

At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.

Boehlert, C. J. (Carl J.); Zocco, T. G. (Thomas G.); Schulze, R. K. (Roland K.); Mitchell, J. N. (Jeremy N.); Pereyra, R. A. (Ramiro A.)

2002-01-01

12

Development of anodic stripping voltammetry for determination of gallium in U Ga alloy  

NASA Astrophysics Data System (ADS)

Deposition potential, deposition time, square-wave frequency, rotation speed of the rotating disc electrode and gallium concentration have been studied in detail, for trace concentration level determination of gallium metal in U Ga alloy by square-wave voltammetry anodic stripping analysis, in 1 M NaClO4 + 0.5 M NaSCN at mercury film electrode (MFE). Optimum conditions have been found for Ga(III) determination by obtaining calibration graphs for the range 1 10 × 10-7 M gallium. Error and standard deviation less than 1% were assessed of this method with all gallium standard solutions. The developed methodology was applied successfully as a subsidiary method for the determination of gallium content in synthetic U Ga samples with very good precision and accuracy (under 1% error and std. dev.).

Bhardwaj, T. K.; Sharma, H. S.; Aggarwal, S. K.

2007-03-01

13

Model for electrical power factor of silicon germanium gallium phosphide alloys  

Microsoft Academic Search

A realistic model for the electrical power factor of silicon germanium-gallium phosphide alloys is developed based on mixed scattering theory which takes into account acoustic phonon scattering and ionized impurity scattering. The model is being used to investigate the effect of high temperature heat treatment on the electrical power factor and the potential for further improvement in thermoelectric properties of

D. M. Rowe; Gao Min

1994-01-01

14

An ultrasonic method of mixing powders of refractory metal dichalcogenides with gallium-base low-melting-point alloys  

Microsoft Academic Search

The investigation has shown that ultrasonic treatment is the only effective mechanical method of mixing the components of systems consisting of tungsten and molybdenum disulfides (or diselenides) and gallium-base low-melting-point alloys. Ultrasonic treatment results in the formation of homogeneous mixtures of MoS2, WS2, MoSe2, and WSe2 with gallium alloys in a wide range of concentrations of the latter component (from

T. A. Lobova; G. A. Shvetsova; S. S. Kiparisov; Yu. R. Smirnov; E. P. Terenin

1977-01-01

15

Anodic polarization behavior and microstructure of a gallium-based alloy.  

PubMed

A gallium-based alloy (GA) that was developed as a substitute for dental amalgam was investigated for anodic polarization behavior in deoxygenated Ringers solution, 37 degrees C. The related microstructures were examined and microanalyses were conducted. Four polarization tests were conducted by scanning from -300mV to +1,000 mV (vs. SCE) at 2 mV/s. Polarization of the first sample (GA-1) was stopped after the first anodic dissolution peak (-100 mV, 1.5-2.0 x 10(-3) A/cm2). The fourth sample (GA-4) was interrupted at the secondary peak (+1000 mV, 0.3 A/cm2). It was found that (1) the early stage of the first peak is related to selective dissolution of divalent tin ions, followed by a dissolution of Ga. Transmission electron diffraction (TED) identified the brown corrosion product as Ga2O3; (2) the GA-4 sample was covered with the white corrosion product of mainly Sn+4, identified as SnO2. In addition, the current density of the GA sample when coupled with a high-copper dental amalgam was 0.03 A/cm2 (with +1,000 mV) at the second peak which was about a ten times lower value than for the uncoupled sample; (3) the uncoupled gallium alloy and gallium alloy coupled with a high-copper dental amalgam showed 10(3)-10(4) times higher anodic current density than that of an uncoupled high-copper dental amalgam, suggesting that the gallium alloy is more corrosion prone. PMID:7988754

Oshida, Y; Moore, B K

1993-07-01

16

Abundance and depth of origin of neutral and ionic clusters sputtered from a liquid gallium-indium eutectic alloy  

SciTech Connect

Neutral and positively charged clusters produced by 4 keV Ar[sup +] ion bombardment of a liquid gallium-indium eutectic alloy have been studied by time-of-flight mass spectrometry coupled with single photon positionization of the neutrals. The abundence distributions for clusters with equal nuclearity are statistical. They confirm a strong indium surface segregation. An increasing gallium content and therefore larger depth of origin, was found for increasing cluster size.

Lill, T.B.; Callaway, W.F.; Pellin, M.J.; Gruen, D.M. (Materials Science, Chemical Technology, and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439 (United States))

1994-09-19

17

[Studies on newly improved gallium alloy as dental restorative material, by addition of SiC whisker and titanium powder].  

PubMed

Studies on new gallium alloy using liquid alloy of Ga-Sn-In which was stable at room temperature and with Ag-Sn-Cu-Pd-Zn alloy as powder, were undertaken. Two kinds of gallium alloy by addition of SiC whisker and titanium powder were made on an experimental basis for the purpose of improving the property of this alloy (reinforced alloy). Physical properties such as compressive strength, diametral tensile strength, dimensional change and chemical properties such as discoloration, corrosion, quantitative analysis by Inductively Coupled Plasma were measured. Furthermore breakage surface of alloy after tensile test was observed with SEM. The effect of adding SiC whisker and titanium powder to gallium alloy was discussed and the conclusions were as follows; 1) Compressive strength: Initial strength decreased due to addition of SiC whisker and titanium powder. However, it showed a tendency to increase as time elapsed. It approached the same degree of compressive strength after 7 days. 2) Diametral tensile strength: The best results were obtained by addition of 1% SiC whisker to gallium alloy and the optimum trituration time was 13 seconds in this study. 3) Dimensional change: Expansion in the dimensional change was observed in all testing groups which was slightly over the limitation of ISO and ADA No.1 specification. 4) Discoloration: In the case with addition of titanium powder to gallium alloy, an improvement of discoloration was manifested in artificial saliva and 1% NaS, especially prominent in the former. The favorable results were obtained by addition of 10% titanium powder to gallium alloy for discoloration tolerance. 5) Corrosion: The corrosion was low in four kinds of test immersion liquid. The best results were obtained by addition of 10% titanium powder to gallium alloy. 6) Quantitative analysis by Inductively Coupled Plasma: The examined amount of Zn dissolved out from core composition was decreased due to addition of titanium powder. An improvement of amount in dissolution of Ga, Sn and In from matrix was recognized. 7) In physical and chemical experiment's results, it was judged that the addition of 0.5-0.7% SiC whisker and 5-10% titanium powder was useful. PMID:2488895

Kim, H W

1989-01-01

18

Thermodynamic properties of lanthanum in gallium-indium eutectic based alloys  

NASA Astrophysics Data System (ADS)

Activity and activity coefficients of lanthanum were determined for the first time in gallium-indium eutectic based alloys in a wide temperature range employing electromotive force method. Activity of ?-La and super cooled liquid lanthanum in Ga-In eutectic based alloys between 573 and 1073 K linearly depends on the reciprocal temperature:lga=5.660-15,352T±0.093 lga=6.074-15,839T±0.093 Activity coefficients of ?-La and super cooled liquid lanthanum in this system at 617-1073 K are described by the following equations:lg?=3.786-12,216T±0.171 lg?=4.199-12,703T±0.171 In addition activity of lanthanum in alloys with In was also determined in the same temperature range.

Shchetinskiy, A. V.; Dedyukhin, A. S.; Volkovich, V. A.; Yamshchikov, L. F.; Maisheva, A. I.; Osipenko, A. G.; Kormilitsyn, M. V.

2013-04-01

19

Solid electrolyte cell studies of solid nickel-gallium alloys  

Microsoft Academic Search

Reversible galvanic cells employing ZrO2-CaO solid electrolytes and either Pt\\/O2 (air) or Ni\\/NiO reference electrodes were used to measure thermodynamic properties of solid Ni-Ga alloys at temperatures\\u000a between 873 and 1100 K. Activities, partial Gibbs energies, and integral Gibbs energies, entropies, and enthalpies have been\\u000a obtained for the a (fcc) solid solution and for the intermediate phases—Ni3Ga, Ni5Ga3, Ni3Ga2, Ni13Ga9,

J. N. Pratt; J. M. Bird

1993-01-01

20

Czochralski growth of gallium indium antimonide alloy crystals  

NASA Astrophysics Data System (ADS)

Attempts were made to grow alloy crystals of Gasb{1-x}Insb{x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to around 2 to 5 mole % InSb were grown from seeds up to around 1 to 2 mole % InSb, which were grown from essentially pure GaSb seeds of the (111) direction. Single crystals were grown with InSb rising from around 2 to 6 mole % at the seed ends to around 14 to 23 mole % InSb at the finish ends. A conical reflector was installed above the melt and coaxially around the growing crystal to help the crystal grow monocrystalline. Floating crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Gasb{1-x}Insb{x}Sb. Crystals close to the targeted composition of 1 mole % InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals around 2 mole % were grown when 4 mole % was targeted. It was observed that mixing occurred between the melts and render the compositions of the melts and hence the resultant crystal unpredictable. The higher density of the growth melt than the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Gasb{1-x}Insb{x}Sb single crystals were grown successfully by pressure-differential technique that a quartz tube was separated into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bisb{1-x}Sbsb{x}. Single crystals of Gasb{1-x}Insb{x}Sb were grown with uniform compositions up to nearly 5 mole % InSb.

Tsaur, Shuenn-Ching

21

Alloying and Structure of Ultrathin Gallium Films on the (111) and (110) Surfaces of Palladium  

PubMed Central

Growth, thermal stability, and structure of ultrathin gallium films on Pd(111) and Pd(110) are investigated by low-energy ion scattering and low-energy electron diffraction. Common to both surface orientations are growth of disordered Ga films at coverages of a few monolayers (T = 150 K), onset of alloy formation at low temperatures (T ? 200 K), and formation of a metastable, mostly disordered 1:1 surface alloy at temperatures around 400–500 K. At higher temperatures a Ga surface fraction of ?0.3 is slightly stabilized on Pd(111), which we suggest to be related to the formation of Pd2Ga bulk-like films. While on Pd(110) only a Pd-up/Ga-down buckled surface was observed, an inversion of buckling was observed on Pd(111) upon heating. Similarities and differences to the related Zn/Pd system are discussed.

2013-01-01

22

Kinetics of growth of indium gallium nitride alloys by MBE and development of polar and non-polar indium gallium nitride MQWs  

NASA Astrophysics Data System (ADS)

InGaN alloys and MQWs constitute the active region of light emitting diodes (LEDs) and lasers emitting in the visible part of the spectrum. In spite of the significant progress over the past several years, the physics related to the growth, structure and optical properties of these alloys is poorly understood. This has prevented the development of efficient emitters in the blue and green part of the spectrum where the indium mol fraction must exceed 15-20%. The difficulty with the growth of these alloys is partly related to solubility of InN in GaN at the usual growth temperatures and partly to significantly higher vapor pressure of nitrogen over InN than GaN. In this dissertation, I addressed the growth, the structure and the optical properties of InGaN alloys and QWs grown along polar and non-polar directions by plasma assisted MBE. The InGaN alloys were grown both in their nitrogen and gallium (indium) polar directions. The incorporation of Indium during growth was investigated in-situ by observing the evolution of reflected high energy electron diffraction (RHEED) patterns as a function of time, and ex-situ by x-ray diffraction studies. Conditions have been identified to grow nitrogen polar InGaN alloys in the entire alloy composition. On the other hand, the highest indium mol fraction achievable for Ga-polar growth was 30%. The difference between these two growth regimes was found to result from differences in the bonding of the two polarities. Study of the optical properties of these materials revealed Stoke's shifts in the emission spectra of 100 meV for N-polar films and up to 420 meV for Ga-polar films consistent with the microstructure identified for each. Polar InGaN MQWs were deposited on c-plane HVPE-grown GaN templates. The emission properties of these MQWs were correlated with various growth parameters by comparing the internal quantum efficiencies (IQEs), which varied from 0.5 to ˜30%. Furthermore, the role of dislocations as non-radiative recombination centers in these MQWs was investigated. Non-polar InGaN MQWs were deposited onto a-plane HVPE-grown GaN templates. These MQWs were found to have IQEs of ˜70%, a result consistent with the suppression of the quantum-confined-Stark-effect (QCSE). Prototype LED structures based on such MQWs were grown and fabricated into 800x800 mum devices. An output power of 14mW at 1A injection current was measured under bare die testing.

Abell, Joshua

23

Study of uranium solubility in gallium-indium eutectic alloy by emf method  

NASA Astrophysics Data System (ADS)

Activity, activity coefficients and solubility of uranium in Ga-In eutectic alloy as well as activity of uranium in U-Ga and U-In alloys were determined between 573 and 1073 K using electromotive force (emf) method.

Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Osipenko, A. G.; Raspopin, S. P.; Kormilitsyn, M. V.

2013-02-01

24

The effect of high-temperature heat treatment on the electrical power factor and morphology of silicon germanium-gallium phosphide alloys  

Microsoft Academic Search

The results of an experimental investigation into the effect of high-temperature heat treatment on the electrical resistivity and Seeback coefficient of silicon germanium-gallium phosphide alloys and the accompanying changes in morphology are reported. Substantial changes in the electrical properties and in morphology were observed after 15 min and 4-h periods of heat treatment, respectively. A less significant decrease in electrical

Gao Min; D. M. Rowe

1991-01-01

25

Thermodynamics of reaction of praseodymium with gallium-indium eutectic alloy  

NASA Astrophysics Data System (ADS)

Thermodynamic properties of Ga-In eutectic alloys saturated with praseodymium were determined for the first time employing the electromotive force method. The equilibrium potentials of the Pr-In alloys saturated with praseodymium (8.7-12.1 mol.% Pr) and Pr-Ga-In alloys (containing 0.0012-6.71 mol.% Pr) were measured between 573-1073 K. Pr-In alloy containing solid PrIn3 with known thermodynamic properties was used as the reference electrode when measuring the potentials of ternary Pr-In-Ga alloys. Activity, partial and excessive thermodynamic functions of praseodymium in alloys with indium and Ga-In eutectic were calculated. Activity (a), activity coefficients (?) and solubility (X) of praseodymium in the studied temperature range can be expressed by the following equations:lga?-Pr(In) = 4.425 - 11965/T ± 0.026.lg?-Pr(Ga-In) = 5.866 - 14766/T ± 0.190.lg??-Pr(Ga-In) = 2.351 - 9996/T ± 0.39.lg&\\HcyPr(Ga-In) = 3.515 - 4770/T ± 0.20.

Melchakov, S. Yu.; Ivanov, V. A.; Yamshchikov, L. F.; Volkovich, V. A.; Osipenko, A. G.; Kormilitsyn, M. V.

2013-06-01

26

Marginal adaptation and micro-porosity of class II restorations of a high copper amalgam and a palladium-free gallium-based alloy.  

PubMed

The aim of the current investigation was to compare the marginal adaptation and internal porosity of a gallium (Ga)-based alloy (Galloy) with a high copper amalgam (Permite C DP) when used in moderately sized conventional class II cavities. Ten dentists placed two restorations of each material in standardized class II cavities in typodont teeth set in a phantom head. The proximal surfaces of the restored teeth were subsequently examined using an optical microscope and colour photographs were taken. The teeth were then serially sectioned before being re-examined microscopically and re-photographed. Three dentists rated the photographs of the restorations on two occasions, 2 weeks apart, for marginal adaptation and internal porosity using a six and five point scoring criteria, respectively. Inter- and intra-examiner agreements were assessed with weighted kappa statistics. The Ga-based alloy exhibited inferior marginal adaptation and a significantly higher level of porosity and internal defects compared with the dental amalgam. Marginal defects were mainly concentrated at the gingival third of the proximal boxes for both alloys. The poor marginal adaptation and extensive internal porosity detected for the Ga-based alloy was attributed to the difficulty in the alloy condensation related mainly to the 'stickiness' of the alloy to the condensers and to the rapid change in the plasticity of the alloy during condensation. This could possibly be a factor in the post-operative complications reported with the clinical use of this alloy. PMID:17168935

Shaini, F J; Wahab, F K; Ellakwa, A E; Shortall, A C C; Fleming, G J P; Marquis, P M

2006-12-01

27

Effect of hydrogen and magnetic field on the mechanical behavior of magnetostrictive iron-gallium alloys  

NASA Astrophysics Data System (ADS)

Magnetostrictive Fe-Ga and other iron-based alloys are candidates for use in sensing, actuation and large-scale energy harvesting applications. Exposure to aqueous electrochemical environments is anticipated in some of these applications which could potentially introduce hydrogen into the alloy and cause severe ductility reduction due to hydrogen embrittlement. These alloys may also be simultaneously exposed to magnetic field. This study therefore examines the effect of hydrogen and magnetic field on the mechanical behavior of these alloys. This study could also provide an understanding of the relationship between hydrogen embrittlement and magnetoelastic behavior in these alloys. In this work, the effect of hydrogen and magnetic field on the fracture behavior of [100]-oriented Fe-17.5 at.% Ga alloy single crystals and polycrystalline Fe-15 at.% Ga alloy were examined. Three-point bend tests and tensile tests were used to study the fracture behavior. Tests were done in different conditions to understand the effect of hydrogen and magnetic field on the fracture behavior of these materials. Hydrogen loading was done by in-situ electrochemical charging and magnetic field was applied to the samples either by using Nd2Fe 14B permanent magnets or by using solenoid coils. Before doing the three-point bend test on the Fe-Ga single crystal samples, tests were done using high-strength AISI 4340 steel to optimize the testing procedures and parameters. In all cases, the samples tested with hydrogen charging show a drastic reduction in ductility and fracture stress values. In the case of [100]-oriented Fe-17.5 at.% Ga alloy single crystal samples tested with hydrogen charging, the presence of applied magnetic field increased the stress required for fracture and a corresponding increase in bending strain values. This is attributed to a decrease of the elastic modulus values on the application of magnetic field in this magnetostrictive alloy. The hydrogen embrittlement was characterized by a change in fracture surface from a ductile type fracture to a brittle cleavage type fracture. Acoustic emission signals collected during the test correspond to the fracture behavior.

Ramanathan, Meenakshisundaram

28

Role of Ga-doping in iron—gallium alloy clusters  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of Fen-mGam (n = 3 ~ 6, m = 0 ~ 2; n = 13, m = 0 ~ 3) alloy clusters have been studied using density functional theory. The substitutional doping is favourable for small clusters with up to six atoms at low Ga concentration and substitutional Ga atoms in 13-atom clusters prefer surface sites. The Ga-doping generally could reduce the energetic stability but enhance the electronic stability of Fe clusters, along with a decrease of the local magnetic moments of Fe atoms around Ga dopants. These findings provide a microscopic insight into Fe—Ga alloys which are well-known magnetostriction materials.

Tang, Pei-Zhe; Liu, Hai-Tao; Zhu, Jie; Wang, Shan-Ying; Duan, Wen-Hui

2012-02-01

29

Measurement of field-dependence elastic modulus of iron-gallium alloy using tensile test  

SciTech Connect

An experimental approach is used to identify Galfenol material properties under dc magnetic bias fields. Dog-bone-shaped specimens of single crystal Fe{sub 100-x}Ga{sub x}, where 18.6{<=}x{<=}33.2, underwent tensile testing along two crystallographic axis orientations, [110] and [100]. Young's modulus and Poisson's ratio sensitivity to magnetic fields and stoichiometry are investigated. Data are presented that demonstrate the dependence of these properties on applied magnetic-field levels and provide a substantial assessment of the trends in material properties for performance of alloys of different stoichiometries under varied operating conditions.

Yoo, Jin-Hyeong; Flatau, Alison B. [University of Maryland, College Park, Maryland 20742 (United States)

2005-05-15

30

Kinetics of growth of indium gallium nitride alloys by MBE and development of polar and non-polar indium gallium nitride MQWs  

Microsoft Academic Search

InGaN alloys and MQWs constitute the active region of light emitting diodes (LEDs) and lasers emitting in the visible part of the spectrum. In spite of the significant progress over the past several years, the physics related to the growth, structure and optical properties of these alloys is poorly understood. This has prevented the development of efficient emitters in the

Joshua Abell

2008-01-01

31

Study of Bulk Modulus in Zincblende Nitrogen-doped Gallium Phosphide Alloys Using Density Functional Theory  

NASA Astrophysics Data System (ADS)

The prospect of solar energy as a renewable resource is ever-increasing. Density functional theory (DFT) calculations can elicit reliable behavior predictions in energy conversion materials to achieve higher efficiencies. Chemical stability of the photo-catalysts in aqueous solution is of particular interest for its long term performances. The bulk modulus is a mechanical property that is a good indicator of material stability. GaP has a low band gap and is a good candidate for use as a photocatalyst for hydrogen evolution by splitting water. Unfortunately, it is not stable and highly susceptible to corrosion over a very short time period, making it unfeasible for long-term use. GaN has too high of a band gap but a good stability factor. While these materials both possess desirable qualities, they cannot be used solitarily. We will report electronic properties and bulk moduli from the total energy calculations of the zincblende and wurtzite species using DFT-GGA and DFT+U as a function of doping concentration x. We will also present the density of states and charge density distribution of the alloy materials to study the localization/delocalization effects of N defects levels and their impact on the alloys' stability.

Butler, Brandon M.; Turner, John A.; Huda, Muhammad N.

2011-03-01

32

Native point defects in indium nitride and indium-rich indium gallium nitride alloys  

NASA Astrophysics Data System (ADS)

The recent discovery of the narrow bandgap of InN of 0.7 eV has attracted strong scientific interests on the fundamental properties and possible applications of InN and its ternary alloys. The first part of this thesis was inspired by the proposal of using InxGa1-x N alloy to build high efficiency solar cell for space applications. To test the irradiation hardness of InN and InxGa 1-xN, we have irradiated numerous samples with energetic particles (1-2 MeV electrons, protons, and 4He+ particles). InN and InxGa1-xN displayed superior radiation hardness over current multi-junction solar cell materials such as GaAs and GaInP in terms of electronic and optical properties. Free electron concentrations in InN and In-rich InxGa 1-xN increased with irradiation dose but saturated at a sufficiently high damage dose. According to the amphoteric defect model, the doping effect and the electron concentration saturation originates from irradiation-induced native donors and Fermi level pinning at the Fermi level stabilization energy (EFS). The EFS, an average energy of all localized native defects, dictates the electronic properties (donor or acceptor) of the native point defects. The electron concentration saturation and Fermi level pinning lead to profound changes in the optical properties. Absorption spectra shift to higher energy due to the conduction band-filling effect (Burstein-Moss shift). Photoluminescence (PL) signals broadened and shifted to higher energy as the k-conservation rule collapsed with irradiation damage. The PL intensity of increased slightly with higher carrier concentration before it became quenched by the irradiation-induced carrier traps. Capacitance-voltage (CV) measurements show that the pinning of the surface Fermi energy at EFS is also responsible for the surface electron accumulation effect in InN and In-rich In xGa1-xN alloys. The second part of this thesis focuses on the hydrostatic pressure dependence of group III-nitride alloys. The hydrostatic pressure dependence of the narrow bandgap of InN, In-rich InxGa1-x N (0 < x ? 0.5), and InyAl 1-yN (y = 0.25) alloys was measured by optical absorption and PL experiments with samples mounted in diamond anvil cells. The pressure coefficient of InN was experimentally determined for the first time to be 3.0+/-0.1 meV/kbar. The PL signal exhibits a much weaker pressure dependence than the direct bandgap, which is attributed to the emission process associated with highly localized states. Using the localized states emission as an energy reference, the deformation potential of the band edges of InN and In0.5Ga0.5N were determined.

Li, Sonny Xiao-Zhe

33

Thermal cnductivity and Lorenz number of plutonium and plutonium-gallium alloys  

SciTech Connect

The thermal diffusivities of Pu, Pu-2.7 at. % Ga, Pu-3.5 at. % Ga, and Pu-6.6 at. % Ga were measured from 25/sup 0/C to around 500/sup 0/C using a laser flash technique and electronic data acquisition. Although the Lorenz number, L, of pure Pu is well below the Sommerfeld value, L/sub 0/, except for the ..cap alpha..-phase, L exceeds L/sub 0/ for the alloys at all temperatures and has a pronounced minimum around 200/sup 0/C. At the lower temperatures we attribute the excess to lattice conduction and at temperature above 200/sup 0/C the excess is attributed to an electronic component. The negative deviation of L from L/sub 0/ for pure Pu is ascribed to a reduction of the electron mobilities in those energy ranges where the 5f bands overlap the conduction bands.

Andrew, J.F.; Klemens, P.G.

1981-01-01

34

Gallium Safety in the Laboratory  

SciTech Connect

A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

Cadwallader, L.C.

2003-05-07

35

Gallium Safety in the Laboratory  

SciTech Connect

A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

Lee C. Cadwallader

2003-06-01

36

Metal organic chemical vapor deposition of indium gallium nitride alloys on nanowire substrates  

NASA Astrophysics Data System (ADS)

Rising environmental concerns due to our rising population and energy demand along with our excessive dependence on fossil fuels has created an urgent need to find clean, renewable and carbon free source of energy. Photoelectrochemical (PEC) water splitting is a clean and carbon free process where hydrogen is produced from water and sunlight using a semiconductor. To date, no material has been found that meets the stringent requirements of band gap, band edge positions and stability for spontaneous water splitting. It is however possible to use two materials to meet the criteria. In this regard, InGaN alloys with indium rich composition are interesting materials. However, very little is understood about the synthesis of thick (˜200--300 nm), single crystal InGaN layers for PEC applications. Heteroepitaxial growth of InGaN films on planar substrates induces phase segregation due to stress. Here, we proposed to investigate the role of nanowires as strain relaxing substrates to mitigate phase segregation. GaN nanowires with controlled orientation and small diameters were synthesized on various substrates by controlling the temperature and material flux to control the nuclei formation. The mechanism to control the growth mode using equilibrium solubility was validated with the III-Sb system. InGaN layers with controlled composition were synthesized on the GaN nanowires in a custom built MOCVD reactor. The InGaN layers are single crystalline, without any phase segregation. It was observed that only nanowires with diameters < 30 nm led to the observation while nanowires with larger diameters (˜ 100 nm) act as planar substrates resulting in polycrystalline growth. The heteroepitaxial growth was observed to evolve from initial InGaN islands coalescing into single crystalline shell on the GaN nanowires. Morphology of the InGaN shells was observed to depend on the orientation of the GaN nanowire substrates with c-GaN nanowires resulting in hexagonal shell while a-GaN nanowires had rectangular shell. We also investigated a novel material system GaSbN using theoretical techniques for its applicability toward PEC water splitting. The electronic structure of GaSbN system with dilute antimony was investigated using theoretical simulations. Results indicate that only very small antimony content (< 10%) is required to achieve the right band gap. Most importantly, the band edges of GaSbN alloy seem to straddle the water splitting potentials that makes it a potential direct water splitting material.

Pendyala, Chandrashekhar

37

Gallium complexes and solvent extraction of gallium  

SciTech Connect

This patent describes a process for recovering gallium from aqueous solutions containing gallium which comprises contacting such a solution with an organic solvent containing at least 2% by weight of a water-insoluble N-organo hydroxamic acid having at least about 8 carbon atoms to extract gallium, and separating the gallium loaded organic solvent phase from the aqueous phase.

Coleman, J.P.; Graham, C.R.; Monzyk, B.F.

1988-05-03

38

Studies of the anodic dissolution of aluminium alloys containing tin and gallium using imaging with a high-speed camera  

Microsoft Academic Search

Imaging with a high-speed camera at a resolution of 10–20?m has been used for the direct observation of the anodic dissolution of aluminium alloys containing Sn and Ga. The imaging allows confirmation that hydrogen bubble evolution occurs from the Sn inclusions within rounded pits during both open circuit corrosion and anodic dissolution. Using microelectrodes with only a few Sn inclusions

Peter R. Birkin; Maria Nestoridi; Derek Pletcher

2009-01-01

39

Influence of dislocations and second phases on the magnetostrictive behavior of iron-gallium and other iron alloy single crystals  

NASA Astrophysics Data System (ADS)

Rare-earth-free Fe-Ga magnetostrictive alloys exhibit an excellent combination of large low-field magnetostriction, strength, ductility, wide operating temperature range, and low cost. Various observations in these and other alpha-Fe-based magnetostrictive alloys suggest that lattice strain modulations that are influenced by solute elements, near neighbor atomic environments around Fe atoms, coherent and incoherent precipitates, and structural defects such as dislocations likely play an important role in their magnetostrictive behavior. In the first part, the effect of dislocations on the magnetostriction of Fe-Ga single crystals was examined. The [001]- and [126]-oriented Fe-20 at.% Ga single crystal samples were deformed in a controlled way to introduce dislocation arrays with two different array geometries. Magnetostriction values showed a much lower decrease after deformation for the case of a [001]-oriented crystal, where eight different slip systems were operative and consequently eight different sets of dislocation arrays are expected. A drastic drop in magnetostriction measured along the sample axis is observed in the sample subjected to a small strain by deformation of a [126]-oriented crystal during which slip occurred on only one slip system. The nature of strain modulation introduced in this case was spatially asymmetric. The [126] deformation was accompanied by an acoustic emission during the formation of slip band. Transmission electron microscopy was carried out to examine the nature of dislocation distribution. The results show that the nature of strain modulation introduced by the dislocation arrays has a strong influence on the magnetostrictive behavior of magnetostrictive alloys. In the second part of this research, the effect of Mo addition to Fe was examined in detail. Addition of Mo to Fe increased the magnetostriction (3/2)lambda100 Fe very rapidly to 137 ppm at 10 at.% Mo, the highest value observed in these alloys. Further Mo additions decreased the magnetostriction. Magnetization data show a drastic drop in magnetization to 63 emu/gm for Fe-20 at.% Mo from 176 emu/gm for Fe-10 at.% Mo suggesting the formation large amounts of nonmagnetic second phase and reduction in total Fe content of the alloy. The drop in magnetostriction at higher Mo contents is associated with the formation of a second phase.

Saha, Biswadeep

40

Bismuth in gallium arsenide: Structural and electronic properties of GaAs{sub 1-x}Bi{sub x} alloys  

SciTech Connect

The structural and electronic properties of cubic GaAs{sub 1-x}Bi{sub x} alloys with bismuth concentration 0.0, 0.25, 0.50, 0.75 and 1.0 are studied using the 'special quasi-random structures' (SQS) approach of Zunger along with the generalized gradient approximation (GGA) and the Engel-Vosko generalized gradient approximation (EV-GGA). The lattice constant, bulk modulus, derivative of bulk modulus and energy gap vary with bismuth concentration nonlinearly. The present calculations show that the band gap decreases substantially with increasing bismuth concentration and that spin-orbit coupling influences the nature of bonding at high Bi concentrations. - Graphical abstract: Bowing effect of spin-orbit split-off band values versus Bi content with and without spin-orbit coupling for GaAs{sub 1-x}Bi{sub x} (at x=0.25, 0.50 and 0.75). Calculations are done with GGA. Highlights: Black-Right-Pointing-Pointer Structural and electronic properties of GaAs{sub 1-x}Bi{sub x} alloys were studied. Black-Right-Pointing-Pointer We present results of lattice constant, energy gap, bulk modulus and derivative. Black-Right-Pointing-Pointer The band gap decreases substantially with increasing Bi concentration. Black-Right-Pointing-Pointer Calculations of the density of states and charge densities are also presented. Black-Right-Pointing-Pointer We have performed calculations without and with spin-orbit coupling.

Reshak, Ali Hussain, E-mail: maalidph@yahoo.co.uk [School of Complex Systems, FFWP-South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Material Engineering, Malaysia University of Perlis, P.O Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia); Kamarudin, H. [School of Material Engineering, Malaysia University of Perlis, P.O Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia); Auluck, S. [National Physical Laboratory Dr. KS Krishnan Marg, New Delhi 110012 (India); Kityk, I.V. [Electrical Engineering Department, Technological University of Czestochowa, Al. Armii Krajowej 17/19, Czestochowa (Poland)

2012-02-15

41

Influence of nitrogen incorporation on the electronic properties of dilute nitride (indium)gallium arsenic nitride alloys  

NASA Astrophysics Data System (ADS)

(In)GaAsN alloys with a few percent N have shown significant promise for a wide range of applications. However, N incorporation degrades the optical and electronic properties of GaAsN, which has not been sufficiently accounted for by any theory. Thus, the objective of this dissertation is to develop an understanding of the formation of N-related extrinsic and intrinsic point defects and their influence on the electronic properties of InGaAsN alloys. The presence of extrinsic N-related point defect, Si-N complexes, is suggested by a decrease in carrier concentration, n, with increasing N-composition in GaAsN:Si films but not modulation-doped heterostructures. For GaAsN:Te (GaAsN:Si), n increases substantially (minimally) with rapid thermal annealing (RTA) T, suggesting a competition between annealing-induced Si-N complex formation and a reduced concentration of N-related traps. Since Si-N complex formation is enhanced for GaAsN:Si growth with the (2 x 4) reconstruction, which has limited group V sites for As-N exchange, the (Si-N)As interstitial pair is identified as the dominant Si-N complex. Finally, using modulation-doped GaAs(N)/AlGaAs heterostructures, neutral scatterers, likely N interstitials, were identified as the dominant source of carrier scattering in the absence of Si-N complexes. For intrinsic N-related defects, we compared GaAsN films before and after RTA. For as-grown GaAs1-xNx films, an onset of a metal-insulator transition (MIT) at a much higher n than that in GaAs is observed, accompanied by a shrinkage of the electron Bohr radius, aB, with increasing x. In addition, the T-dependence of n for T>150K suggests the presence of a N-induced electron trapping level below the GaAsN CB edge, accompanied by a persistent photoconductivity (PPC) effect. After RTA, a transition occurs in the low T transport mechanism from hopping to extended band conduction, the T-dependence of n is suppressed, and the PPC effect vanishes. Interestingly, NRA reveals an RTA-induced decrease in N interstitial fraction, f int; the corresponding signatures for the reduction in fint are also identified in Raman spectra. Thus, it is likely that N interstitials are responsible for the MIT, the a B shrinkage, the N-induced trapping level, and the PPC effect. Thus, N interstitials are the dominant form of intrinsic N defects in GaAsN.

Jin, Yu

42

Gallium poisoning: a rare case report.  

PubMed

The authors present a case of a college student who suffered acute gallium poisoning as a result of accidental exposure to gallium halide complexes. This is extremely rare and has never been reported in the literature. Acute symptoms after the incident, which initially presented as dermatitis and appeared relatively not life-threatening, rapidly progressed to dangerous episodes of tachycardia, tremors, dyspnea, vertigo, and unexpected black-outs. Had there been effective emergency medical care protocols, diagnostic testing, treatment and antidotes, the latent manifestations of irreversible cardiomyopathy may have been prevented. Given how quickly exposure led to morbidity, this article aims to raise an awareness of the toxic potential of gallium. This has particular relevance for workers involved in the production of semiconductors where there is a potential for accidental exposure to gallium by-products during device processing. It may also have implications for dentists who use gallium alloys to replace mercury containing amalgam. In the absence of threshold limit values and exposure limits for humans, as well as emergency medical guidelines for treatment of poisoning, the case calls on the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration to establish guidelines and medical management protocols specific for gallium. PMID:22024274

Ivanoff, Chris S; Ivanoff, Athena E; Hottel, Timothy L

2011-10-18

43

Orthodontic silver brazing alloys.  

PubMed

Orthodontic silver brazing alloys suffer from the presence of cadmium, excessive flow temperatures, and crevice corrosion on stainless steel. Seven alloys were examined. Two alloys contained cadmium. The lowest flow temperature observed was 629 degrees C for a cadmium alloy and 651 degrees C for two cadmium free alloys. Three alloys had corrosion resistance superior to the other solders. Addition of low melting temperature elements gallium and indium reduced flow temperature in some cases but produced brittleness in the brazing alloy. PMID:2576971

Brockhurst, P J; Pham, H L

1989-10-01

44

Compatibility of ITER candidate structural materials with static gallium  

SciTech Connect

Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400{degrees}C, corrosion rates are {approx}4.0, 0.5, and 0.03 mm/yr for type 316 SS, Inconel 625, and Nb-5 Mo- 1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than nickel. The corrosion rates at 400{degrees}C are {ge}88 and 18 mm/yr, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400{degrees}C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The solubility data for pure metals and oxygen in gallium are reviewed. The physical, chemical, and radioactive properties of gallium are also presented. The supply and availability of gallium, as well as price predictions through the year 2020, are summarized.

Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

1993-12-01

45

Gallium-cooled liquid metallic-fueled fast reactor  

Microsoft Academic Search

We have examined the effects on core characteristics of using two different types of Pu-based metallic alloy fuels in the gallium-cooled fast reactor core. In the proposed concept, the liquid metal fast nuclear reactor uses metallic fuel in the liquid phase and gallium coolant at high temperature (inlet 1700K, outlet 1900K). The liquid fuel is continuously supplied to the reactor

T. Sawada; A. Netchaev; H. Ninokata; H. Endo

2000-01-01

46

Investigations in gallium removal  

SciTech Connect

Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated.

Philip, C.V.; Pitt, W.W. [Texas A and M Univ., College Station, TX (United States); Beard, C.A. [Amarillo National Resource Center for Plutonium, TX (United States)

1997-11-01

47

Reversible expansion of gallium-stabilized (delta)-plutonium  

SciTech Connect

It is shown that the transient expansion of plutonium-gallium alloys observed both in the lattice parameter as well as in the dimension of a sample held at ambient temperature can be explained by assuming incipient precipitation of Pu{sub 3}Ga. However, this ordered {zeta}-phase is also subject to radiation-induced disordering. As a result, the gallium-stabilized {delta}-phase, being metastable at ambient temperature, is driven towards thermodynamic equilibrium by radiation-enhanced diffusion of gallium and at the same time reverted back to its metastable state by radiation-induced disordering. A steady state is reached in which only a modest fraction of the gallium present is arranged in ordered {zeta}-phase regions.

Wolfer, W G; Oudot, B; Baclet, N

2006-02-27

48

Thermodynamic properties of uranium in Ga–In based alloys  

NASA Astrophysics Data System (ADS)

Activity of uranium was determined in gallium, indium and gallium–indium eutectic (21.8 wt.% In) based alloys between 573 and 1073 K employing the electromotive force method. In two-phase U–Ga–In alloys, uranium forms the intermetallic compound UGa3. Activity coefficients and solubility of uranium in Ga–In eutectic were also determined in the same temperature range. Partial thermodynamic functions of ?-U in saturated alloys with gallium, indium and Ga–In eutectic were calculated.

Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Melchakov, S. Yu; Shchetinskiy, A. V.; Osipenko, A. G.; Kormilitsyn, M. V.

2013-07-01

49

Effects of gallium alloy content and the geometrical confinement on effective exciton g-factor in a III-V semiconductor quantum dot  

NASA Astrophysics Data System (ADS)

Effective exciton-g factor as functions of dot radius and Ga alloy content in a GaxIn1-xAs/GaAs quantum dot is computed. The computations are included with the effect of mass anisotropy and the non-parabolicity of the conduction band. The dependence of excitonic binding energy with respect to the dot radius is investigated for various composition of Ga alloy content.

Senthilkumar, N. R.; Peter, A. John

2013-02-01

50

Properties of gallium arsenide  

SciTech Connect

Properties of Gallium Arsenide' is a handbook of evaluated numeric data and reviewed knowledge distilled by those working at the frontiers of gallium arsenide research. In addition to providing numeric data on basic physical, electronic and optical properties, the book covers many device-related aspects of gallium arsenide. Carrier attributes (ionisation coefficients, concentration, mobility, diffusion etc), deep levels and defects are surveyed and related to the various growth techniques such as MBE, VPE, and MOCVD. Sections on surface structure, oxidation, interfaces and etching are of particular relevance to integrated circuit research. Especially important in the race to achieve commercially usable samples is a state-of-the-art survey on the infra-red imaging of defects in semi-insulating gallium arsenide produced by the liquid-encapsulated Czochralski process.

Not Available

1985-01-01

51

Interactions of Zircaloy Cladding with Gallium: Final Report  

SciTech Connect

The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fhel, on cladding material performance. Three previous repmts"3 identified several compatibility issues relating to the presence of gallium in MOX fuel and its possible reaction with fiel cladding. Gallium initially present in weapons-grade (WG) plutonium is largely removed during processing to produce MOX fhel. After blending the plutonium with uranium, only 1 to 10 ppm gallium is expected in the sintered MOX fuel. Gallium present as gallium oxide (G~OJ could be evolved as the suboxide (G~O). Migration of the evolved G~O and diffusion of gallium in the MOX matrix along thermal gradients could lead to locally higher concentrations of G~03. Thus, while an extremely low concentration of gallium in MOX fiel almost ensures a lack of significant interaction of gallium whh Zircaloy fhel cladding, there remains a small probability that corrosion effects will not be negligible. General corrosion in the form of surface alloying resulting from formation of intermetallic compounds between Zircaloy and gallium should be ma& limited and, therefore, superficial because of the expected low ratio of gallium to the surface area or volume of the Zircaloy cladding. Although the expected concentration of gallium is low and there is very limited volubility of gallium in zirconium, especially at temperatures below 700 "C,4 grain boundary penetration and liquid metal embrittlement (LME) are forms of localized corrosion that were also considered. One fuel system darnage mechanism, pellet clad interaction, has led to some failure of the Zircaloy cladding in light-water reactors (LWRS). This has been attributed to stresses in the cladding and one or more aggressive fission products. Stress corrosion cracking by iodines' 6 and LME by cadmium7>8 have been reported, and it is known that Zircaloy can be embrittled by some low-melting metals, (e.g., mercury).g LME is a form of environmentally induced embrittlement that can induce cracking or loss of ductility. LME requties wetting and a tensile stress, but it does not require corrosion penetration. Experimentally, it has been demonstrated that gallium can cause embrittlement of some alloys (e.g., aluminum) at low temperatures,'"' ] ] but experiments relative to LME of zirconium by gallium have been limited and inconclusive.*2 This report describes a series of tests designed to establish the effects of low levels of residual gallium in WG-MOX fhel on its compatibility with Zircaloy. In addition, to establish damage mechanisms it was important to understand types of cladding interactions and available stiety margins with respect to gallium concentration.

D.F. Wilson; E.T. Manneschmidt; J.F. King; J.P. Strizak; J.R. DiStefano

1998-09-01

52

Thermochemical behavior of gallium in weapons-material-derived mixed-oxide light water reactor (LWR) fuel  

Microsoft Academic Search

The use of weapons-derived plutonium in light water reactor (LWR) fuel must consider the effects of up to 1 mass% of gallium that is used in weapons plutonium alloy. The potential effects of this residual gallium have been examined for 5% PuOâ-95% UOâ from a thermochemical standpoint. The state and effect of gallium in the fuel are predicted, based on

Theodore M. Besmann

1998-01-01

53

Probing the effects of surfactant monolayers on gas- liquid collisions: Scattering studies of argon and xenon atoms striking dilute bismuth:gallium alloys  

NASA Astrophysics Data System (ADS)

Atomic beam scattering experiments are used to determine the ways in which surfactant Bi atoms alter energy transfer and scattering direction in collisions between Ar and Xe atoms and two dilute Bi:Ga alloys (0.02 and 0.2 atom% Bi in Ga). The Bi surface coverage of the dilute Bi:Ga solutions is measured with Auger Electron Spectroscopy (AES) and ranges from <1% at 673 K (0.02% Bi:Ga) to 98% at 313 K (0.2% Bi:Ga) of a Bi monolayer. The atomic beam scattering experiments show that surface Bi atoms reduce gas-liquid energy transfer between 92 kJ/mol Ar and 190 kJ/mol Xe atoms and the dilute alloys. The energy transfers take on pure Bi-like values at high Bi surface coverages, pure Ga-like values at low Bi surface coverages, and increase smoothly between the extremes of Bi-rich and Ga-rich surfaces. Surface Bi atoms are less effective at inhibiting Ar and Xe energy transfer when the incident energies of the gases are lowered (at incident energies of <30 kJ/mol for Ar and <75 kJ/mol for Xe). The effect of surface Bi atoms on the atomic-scale corrugation of the Bi, Ga, and Bi:Ga surfaces is investigated by measuring the Ar and Xe scattering intensity at ?inc = ? fin = 55° as a function of liquid temperature. The scattering intensities suggest that pure Ga presents a smoother liquid surface than either pure Bi or the low temperature (monolayer covered) alloy and that raising the temperature of the pure liquids increases surface roughness. The Ar and Xe intensities from the dilute Bi:Ga alloys suggest that the alloy surface is initially roughened as the temperature is increased but then becomes smoother at higher temperatures as surface Bi atoms are replaced with Ga atoms.

Morgan, Jason Aaron

54

Transport properties of proton-irradiated gallium nitride-based two-dimensional electron-gas system  

Microsoft Academic Search

A two-dimensional electron gas system (2DEG) is formed at the interface when a ternary alloy of aluminum gallium nitride is grown on gallium nitride. Very high carrier density can be achieved in these systems due to the strong piezoelectric and pyroelectric properties of the nitrides. The device was grown by molecular beam epitaxy and magnetron sputtering epitaxy. Through resistivity and

François Gaudreau; Patrick Fournier; Cosmo Carlone; Shyam M. Khanna; Haipeng Tang; Jim Webb; Alain Houdayer

2002-01-01

55

Gallium Phosphide and the Gallium Arsenide-Gallium Phosphide System, Data Sheets.  

National Technical Information Service (NTIS)

These data sheets present a compilation of a wide range of electrical, optical and energy values for gallium phosphide and the gallium arsenidegallium phosphide system in bulk and film form. Electrical properties include lifetime and thermoelectric effect...

M. Neuberger

1965-01-01

56

Magnetostriction and Magnetic Heterogeneities in Iron-Gallium  

SciTech Connect

Iron-gallium alloys Fe{sub 1-x}Ga{sub x} exhibit an exceptional increase in magnetostriction with gallium content. We present small-angle neutron scattering investigations on a Fe{sub 0.81}Ga{sub 0.19} single crystal. We uncover heterogeneities with an average spacing of 15 nm and with magnetizations distinct from the matrix. The moments in and around the heterogeneities are observed to reorient with an applied magnetic field or mechanical strain. We discuss the possible roles played by nanoscale magnetic heterogeneities in the mechanism for magnetostriction in this material.

Laver, M. [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH 5232 Villigen (Switzerland); Materials Research Division, Risoe DTU, Technical University of Denmark, DK-4000 Roskilde (Denmark); Nano-Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Koebenhavn (Denmark); Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (United States); Mudivarthi, C.; Cullen, J. R.; Wuttig, M. [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (United States); Flatau, A. B. [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (United States); Department of Aerospace Engineering, University of Maryland, College Park, Maryland 20742 (United States); Chen, W.-C. [NIST Center for Neutron Research (NCNR), Gaithersburg, Maryland 20899 (United States); Indiana University, Bloomington, Indiana 47408 (United States); Watson, S. M. [NIST Center for Neutron Research (NCNR), Gaithersburg, Maryland 20899 (United States)

2010-07-09

57

Resistivity of the liquid gallium-lead miscibility gap system  

NASA Astrophysics Data System (ADS)

We present our electrical resistivity measurements of the gallium-lead system which shows a very large miscibility gap between 2.4 and 94.5 at. % lead with a critical temperature of 606 °C and composition of 40 at. % lead. A small negative deviation of the experimental temperature coefficient of the resistivity (TCR) appears near the critical composition of the alloy. The resistivity of the alloys is interpreted and discussed in terms of the extended Faber-Ziman formula using the t-matrix formalism with hard-sphere and experimental (for pure metals only) structure factors. An approach is proposed, taking into account the information given by the experimental density of states which allowed us to explain the resistivity of pure lead and that of the liquid gallium-lead alloys. As a conclusion it was shown that two electrons in the conduction band of liquid lead better explain the experimental resistivity than four electrons.

Abdellah, A. Ben; Gasser, J. G.; Makradi, A.; Grosdidier, B.; Hugel, J.

2003-11-01

58

Gallium Phosphide Photodiode Development.  

National Technical Information Service (NTIS)

The specific objectives of this program were to fabricate, test and deliver five single-element (detector size 0.01 x 0.01 inch) gallium phosphide (GaP) photovoltaic detectors with performance design goals (for each element) of eta > 30% and NEP < or = 2....

A. M. Chiang R. Rotolante

1977-01-01

59

Growth of (indium,aluminum)gallium nitride alloys by RF-plasma assisted molecular beam epitaxy for application in high electron mobility transistor structures  

NASA Astrophysics Data System (ADS)

In this thesis work, growth of (In,Al)GaN alloys by molecular beam epitaxy (MBE) was investigated with the goal of developing these materials for application in high electron mobility transistor structures (HEMTs). Growth of InGaN alloys by MBE was investigated in detail with the objective of implementing InGaN channels into HEMT structures to improve device performance. A growth diagram for InGaN growth based on III/V ratio during growth was developed. Control of indium composition was studied in detail and found to be highly dependent upon several growth parameters. Systematic studies resulted in demonstration of complete compositional control during growth of InGaN across the entire compositional range. Implementation of these layers into HEMT structures yielded inferior device properties due to an extremely high level of unintentional background carriers in the InGaN channel. Transport measurements were done on bulk InGaN for the first time demonstrating carrier concentrations as high as 1018 cm-2. An all-MBE growth process for AlGaN/GaN HEMTs on SiC was also developed utilizing an AlN nucleation layer and a two-step growth process for the GaN to reduce and control threading dislocation density. The GaN growth process was structurally and electrically optimized to achieve semi-insulating HEMT buffers. Two methods were developed to reduce buffer leakage. The first was through implementation of carbon doping via CBr4, and the second was by optimization of the AlN nucleation layer growth conditions in unintentionally doped (carbon-free) structures. Optimization of the direct-growth process and elimination of buffer leakage led to record output power densities in MBE-grown AlGaN/GaN HEMTs and device performance which is on par with state-of-the art HEMTs grown by metalorganic chemical vapor deposition (MOCVD).

Poblenz, Christiane

60

Gallium-containing anticancer compounds  

PubMed Central

There is an ever pressing need to develop new drugs for the treatment of cancer. Gallium nitrate, a group IIIa metal salt, inhibits the proliferation of tumor cells in vitro and in vivo and has shown activity against non-Hodgkin’s lymphoma and bladder cancer in clinical trials. Gallium can function as an iron mimetic and perturb iron-dependent proliferation and other iron-related processes in tumor cells. Gallium nitrate lacks cross resistance with conventional chemotherapeutic drugs and is not myelosuppressive; it can be used when other drugs have failed or when the blood count is low. Given the therapeutic potential of gallium, newer generations of gallium compounds are now in various phases of preclinical and clinical development. These compounds hold the promise of greater anti-tumor activity against a broader spectrum of cancers. The development of gallium compounds for cancer treatment and their mechanisms of action will be discussed.

Chitambar, Christopher R

2013-01-01

61

Compatibility of ITER candidate materials with static gallium  

SciTech Connect

Corrosion tests have been conducted to determine the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor (ITER) first wall/blanket systems, e.g., Type 316 stainless steel (SS), Inconel 625, and Nb-5 Mo-1 Zr. The results indicate that Type 316 SS is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400 C, corrosion rates for Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy are {approx} 4.0, 0.5, and 0.03 mm/yr, respectively. Iron, nickel, and chromium react rapidly with gallium. Iron shows greater corrosion than nickel at 400 C ({ge} 88 and 18 mm/yr, respectively). The present study indicates that at temperatures up to 400 C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The growth of intermetallic compounds may control the overall rate of corrosion.

Luebbers, P.R.; Chopra, O.K. [Argonne National Lab., IL (United States). Energy Technology Div.

1995-09-01

62

Gallium interactions with Zircaloy  

SciTech Connect

This study focuses on the effects of gallium ion implantation into zircaloy cladding material to investigate the effects that gallium may have in a reactor. High fluence ion implantation of Ga ions was conducted on heated Zircaloy-4 in the range of 10{sup 16}--10{sup 18} Ga ions/cm2. Surface effects were studied using SEM and electron microprobe analysis. The depth profile of Ga in the Zircaloy was characterized with Rutherford backscattering and SIMS techniques. Results indicate that the Zirc-4 is little affected up to a fluence of 10{sup 17} Ga ions/cm{sup 2}. After implantation of 10{sup 18} Ga ions/cm{sup 2}, sub-grain features on the order of 2 {micro}m were observed which may be due to intermetallic compound formation between Ga and Zr. For the highest fluence implant, Ga content in the Zirc-4 reached a saturation value of between 30 and 40 atomic %; significant enhanced diffusion was observed but gallium was not seen to concentrate at grain boundaries.

Woods, A.L. [ed.; West, M.K. [Texas A and M Univ., College Station, TX (United States). Dept. of Nuclear Engineering

1999-01-01

63

Oxidative dissolution of gallium arsenide and separation of gallium from arsenic  

SciTech Connect

The method of dissociating gallium arsenide into a gallium-containing component and an arsenic-containing component, is described which comprises contacting the gallium arsenide with an oxidizing agent and a liquid comprising hydroxamic acid to convert the gallium to a gallium-hydroxamic acid complex and to oxidize the arsenic to a positive valence state.

Coleman, J.P.; Monzyk, B.F.

1988-07-26

64

High quality indium arsenide and related alloys grown on gallium phosphide substrates using a novel liquid phase-molecular beam epitaxy technique  

NASA Astrophysics Data System (ADS)

This thesis emphasizes on the process of making high quality InAs and related alloys on GaP substrates despite the existence of an 11% lattice mismatch. In particular, this work presents the invention and development of a novel Liquid Phase-Molecular Beam Epitaxy (LP-MBE) growth technique. The LP-MBE works by growing a thin (25--50A) In-stabilized InAs initial layer on GaP at around 500°C, followed by the growth of As-stabilized InAs at the same substrate temperature. The arsenic flux is selected such that the InAs growth occurs near the In-to-As stabilized reconstruction transition region; i.e. just slightly In-rich and slightly arsenic-rich during the growth of In-stabilized InAs initial layer and normal As-stabilized InAs respectively. This growth technique shows a reduced InAs surface defect density by one order of magnitude to ˜103 cm-2. The InAs surface is free of cross-hatch as observed by Nomarski phase-contrast microscopy. The surface roughness of InAs has been improved to 13.67A as measured by AFM. HRTEM of InAs/GaP interface shows possible formation of InxGa1-xAsyP1-y graded layer which leads to these improvements. Phase diagram modelings and several ways to test the existence of this graded layer are discussed. It is also shown that incorporating the Strained-Layer Superlattice (SLS) that acts as dislocation bender into LP-MBE grown InAs/GaP improves InAs electrical properties. The background carrier concentration of InAs is reduced to about 3 x 1016 cm-3 and an electron mobility of over 12,000 cm2/V-s has been achieved, as measured by Hall effect. ECV measurements also confirm these improvements. In addition, it is also demonstrated that LP-MBE method can be used to grow other lattice-mismatched materials such as InP on GaP with a 7% lattice mismatch. This work is patent pending.

Yulius, Aristo

65

Hepatic photopenia in gallium imaging  

Microsoft Academic Search

Although Ga-67 has been used extensively in imaging many different conditions, much is yet unknown about the mechanisms by which gallium concentrates preferentially in tissues such as the liver. This paper reports three patients with markedly diminished hepatic uptake of gallium. The cases are examined in light of published data demonstrating such factors as transferrin levels, radiation, and chemotherapeutic agents

ANNE M. GLASER; DAVID C. P. CHEN; MICHAEL E. SIEGEL

1988-01-01

66

Gallium scintigraphy in Hansen's disease  

Microsoft Academic Search

Gallium 67 imaging was used in 12 patients with documented Hansen's disease undergoing treatment or not, in an attempt to determine the pattern of the disease. Diagnosis was confirmed by histopathology in all patients. The Mitsuda reaction was seen in all patients. Specific nuclear studies were performed when needed to evaluate particular organs better. Gallium 67 images show homogeneous, diffuse

Francisco José H. N. Braga; Elaine B. Araújo; Edwaldo E. Camargo; Leontina C. M. Tedesco-Marchesi; Maria Cecilia M. Rivitti; Hateme Bouladour; Pierre Galle

1991-01-01

67

Electrospun Gallium Nitride Nanofibers  

SciTech Connect

The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH{sub 3} flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

Melendez, Anamaris; Morales, Kristle; Ramos, Idalia [University of Puerto Rico at Humacao, Humacao (Puerto Rico); Campo, Eva [Centre Nacional de Microelectronica, Barcelona (Spain); Santiago, Jorge J. [University of Pennsylvania, Philadelphia (United States)

2009-04-19

68

A gallium arsenide power rectifier  

Microsoft Academic Search

In this paper we will describe the fabrication of a gallium arsenide rectifier with a 10 ampere forward current capability, and reverse breakdowns of 40-100 volts. These units are fabricated by a manganese diffusion into gallium arsenide having a prediffusion carrier concentration of about3 times 10^{16}\\/cm3. The diffusion techniques and evaluation will be described. Problems of conversion toward p-type will

L. D. Armstrong; P. Kuznetzoff

1960-01-01

69

Gallium nitride electronics: Watt is the limit? [summary of GaN semiconductor devices  

Microsoft Academic Search

Summary form only given. This work presents a summary of the use of gallium nitride and its alloys in the development of semiconductor devices. It begins with a description of the HEMT and its use in microwave and power switching applications. Then follows a brief examination of MOSHFETs, MISHFETs and MISFETs. HBTs are discussed, along with the problems of poor

U. K. Mishra

2004-01-01

70

The Gallium Melting-Point Standard.  

National Technical Information Service (NTIS)

This Special Publication contains a series of papers published in Clinical Chemistry concerning the Bureau's temperature measurement system, the gallium melting-point as a thermometric fixed-point, how the gallium melting-point fits into the measurement s...

B. W. Mangum D. D. Thornton

1977-01-01

71

Gallium-67 localization in herpetic skin lesion.  

PubMed

Previous cases of gallium localization in various cutaneous lesions have been reported, including sporotrichosis, acne vulgaris, sarcoid, lymphoma, and exfoliative erythroderma. This is a report of a case of gallium localization in cutaneous lesions of herpes zoster. PMID:3180617

Acio, E R; Balasubramanian, N; Vieras, F; Smith, J J

1988-09-01

72

Effect of gallium on bone mineral properties  

Microsoft Academic Search

Summary  Gallium nitrate is biologically active in blocking bone rsorptionin vitro as well asin vivo. Administration of gallium nitrate to growing rats results in a dose-dependent accumulation of low levels of gallium in bone\\u000a that is associated with specific changes in the mineral properties of bone. To elucidate in greater detail the changes induced\\u000a by gallium, the properties of whole and

Mary A. Repo; Richard S. Bockman; Foster Betts; Adele L. Boskey; Nancy W. Alcock; Raymond P. Warrell

1988-01-01

73

Examples of liquiq metal embrittlement in industrial aluminium alloys  

NASA Astrophysics Data System (ADS)

Liquid metal embrittlement (LME) phenomena were investigated in two industrial aluminium alloys. Gallium penetration in 7010 alloys was systematically investigated to shed light on the effect of microstructure and plasticity ahead of the crack tip. Hot temperature shortness in 5083 alloy is given as an example of cleavage induced by LME.

Bréchet, Y.; Rodine, A.; Véron, M.; Péron, S.; Deschamps, A.

2002-09-01

74

Potential effects of gallium on cladding materials  

SciTech Connect

This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

1997-10-01

75

Atomic scale characterization of threading dislocations in gallium nitride  

NASA Astrophysics Data System (ADS)

Gallium nitride is a semiconducting material that emits light in the blue/green region of the visible spectrum. The development of optoelectronic devices that utilize this part of the spectrum will revolutionize many aspects of the lighting industry by providing efficient, long-lasting sources of light. Furthermore, by alloying gallium nitride with other elements such as indium and aluminum and creating emission across the whole visible spectrum, it is even possible to create white light sources. Although devices utilizing the alloys of gallium nitride are already being fabricated, there are still major issues concerning the materials performance that have yet to be fully understood---issues that are limiting the full realization of the technology. In particular, perhaps the most intriguing issue from a fundamental materials physics perspective, is that devices are known to function despite a density of threading dislocations that is high enough to inhibit emission in other similarly structured semiconducting materials. The aim of this Ph.D. dissertation is to explore the atomic scale origins of the intriguing properties of dislocations in gallium nitride. The analysis of the three types of threading dislocations present in the active layers of gallium nitride based devices, edge, screw and mixed, has been performed utilizing state-of-the-art imaging and analytical techniques in the scanning transmission electron microscope. This dissertation discusses the structural properties of all the cores determined using the incoherent Z-contrast imaging method and includes the first experimental determination of the core structure of mixed dislocations (including the case where it dissociates into partials). The composition of the cores and their electronic properties has been determined experimentally using electron energy loss spectroscopy, which has provided the first direct evidence that the electronic properties of dislocation cores can be controlled by the presence of oxygen impurities. The interpretation of the electronic structure changes observed at the cores has been supported by detailed simulations using both the multiple scattering methodology and ab-initio density functional theory. The correlation between these computational methods and the atomic scale experimental analysis is explored with reference to the development of new levels of resolution in aberration corrected and monochromated electron microscopes.

Arslan, Ilke

76

Surface Passivation of Gallium Arsenide.  

National Technical Information Service (NTIS)

The surface passivation of Si doped (100) n-type gallium arsenide (GaAs) by chemical treatment with phosphoric acid (H3P04), phosphorus trichloride (PCl3), and sodium sulfide (Na2S.9H2O) was investigated using room temperature photoluminescence (PL) and a...

R. J. Racicot

1988-01-01

77

Gallium scan in intracerebral sarcoidosis  

SciTech Connect

Sarcoidosis involving the nervous system probably occurs in about 4% of patients. The usefulness of brain scintigraphy in these cases has been suggested. In this case of cerebral sarcoid granuloma, gallium imaging demonstrated the lesion before treatment and showed disappearance of the lesion after corticosteroid treatment, which correlated with the patient's clinical improvement.

Makhija, M.C.; Anayiotos, C.P.

1981-07-01

78

Lewis-Acid/Base Effects on Gallium Volatility in Molten Chlorides  

SciTech Connect

It has been proposed that GaCl{sub 3} can be removed by direct volatilization from a Pu-Ga alloy that is dissolved in a molten chloride salt. Although pure GaCl{sub 3} is quite volatile (boiling point, 201 C), the behavior of GaCl{sub 3} dissolved in chloride salts is different due to solution effects and is critically dependent on the composition of the solvent salt (i.e., its Lewis-acid/base character). In this report, the behavior of gallium in prototypical Lewis-acid and Lewis-base salts is compared. It was found that gallium volatility is suppressed in basic melts and enhanced in acidic melts. The implications of these results on the potential for simple gallium removal in molten salt systems are significant.

Williams, D.F.

2001-02-26

79

40 CFR 721.10391 - Copper gallium indium selenide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Copper gallium indium selenide. 721.10391...Chemical Substances § 721.10391 Copper gallium indium selenide. (a) Chemical...The chemical substance identified as copper gallium indium selenide (PMN...

2013-07-01

80

Scintigraphie au gallium-67 et coeur. (Gallium-67 scintigraphy and the Heart).  

National Technical Information Service (NTIS)

Although gallium-67 was initially used for tumor imaging, clinical studies suggested its potential use as a method of detecting occult inflammatory lesions. The demonstration of diffuse myocardial uptake of gallium-67 during Lyme disease myocarditis is co...

D. Garayt

1987-01-01

81

Radiation Effects on Gallium Arsenide Phosphide and Gallium Phosphide Schottky Barrier Diodes.  

National Technical Information Service (NTIS)

Gallium arsenide phosphide (GaAsP) and gallium phosphide (GaP) Schottky barrier diodes were fabricated and the transient ionizing and stable fast neutron radiation effects on these diodes were determined. (Author)

D. A. Neamen W. W. Grannemann

1971-01-01

82

In vitro bio-functionality of gallium nitride sensors for radiation biophysics.  

PubMed

There is an increasing interest in the integration of hybrid bio-semiconductor systems for the non-invasive evaluation of physiological parameters. High quality gallium nitride and its alloys show promising characteristics to monitor cellular parameters. Nevertheless, such applications not only request appropriate sensing capabilities but also the biocompatibility and especially the biofunctionality of materials. Here we show extensive biocompatibility studies of gallium nitride and, for the first time, a biofunctionality assay using ionizing radiation. Analytical sensor devices are used in medical settings, as well as for cell- and tissue engineering. Within these fields, semiconductor devices have increasingly been applied for online biosensing on a cellular and tissue level. Integration of advanced materials such as gallium nitride into these systems has the potential to increase the range of applicability for a multitude of test devices and greatly enhance sensitivity and functionality. However, for such applications it is necessary to optimize cell-surface interactions and to verify the biocompatibility of the semiconductor. In this work, we present studies of mouse fibroblast cell activity grown on gallium nitride surfaces after applying external noxa. Cell-semiconductor hybrids were irradiated with X-rays at air kerma doses up to 250 mGy and the DNA repair dynamics, cell proliferation, and cell growth dynamics of adherent cells were compared to control samples. The impact of ionizing radiation on DNA, along with the associated cellular repair mechanisms, is well characterized and serves as a reference tool for evaluation of substrate effects. The results indicate that gallium nitride does not require specific surface treatments to ensure biocompatibility and suggest that cell signaling is not affected by micro-environmental alterations arising from gallium nitride-cell interactions. The observation that gallium nitride provides no bio-functional influence on the cellular environment confirms that this material is well suited for future biosensing applications without the need for additional chemical surface modification. PMID:22771805

Hofstetter, Markus; Howgate, John; Schmid, Martin; Schoell, Sebastian; Sachsenhauser, Matthias; Adigüzel, Denis; Stutzmann, Martin; Sharp, Ian D; Thalhammer, Stefan

2012-07-03

83

Heteroepitaxial growth of gallium phosphide on silicon  

Microsoft Academic Search

A new method of growing gallium phosphide on a silicon substrate is presented. The method includes an extra but simple process\\u000a of depositing a thin phosphorus layer on a silicon substrate prior to the growth of gallium phosphide by a so-called halide\\u000a transport method. Electronic and optical properties of the heterojunctions indicate that the interfaces between the gallium\\u000a phosphide layers

T. Katoda; M. Kishi

1980-01-01

84

Collector for recovering gallium from weapons plutonium  

SciTech Connect

Currently, the separation of gallium from weapons plutonium involves the use of aqueous processing using either solvent extraction of ion exchange. However, this process generates significant quantities of liquid radioactive wastes. A Thermally Induced Gallium Removal process, or TIGR, developed by researchers at Los Alamos National Laboratories, is a simpler alternative to aqueous processing. This research examined this process, and the behavior of gallium suboxide, a vapor that is swept away by passing hydrogen/argon over gallium trioxide/plutonium oxide heated at 1100 C during the TIGR process. Through experimental procedures, efforts were made to prevent the deposition of corrosive gallium onto furnace and vent surfaces. Experimental procedures included three options for gallium removal and collection: (1) collection of gallium suboxide through use of a cold finger; (2) collection by in situ air oxidation; and (3) collection of gallium on copper. Results conclude all three collection mechanisms are feasible. In addition, gallium trioxide exists in three crystalline forms, and each form was encountered during each experiment, and that each form will have a different reactivity.

Philip, C.V.; Anthony, R.G.; Chokkaram, S. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemical Engineering

1998-09-01

85

Ion Implantation in Gallium Arsenide  

Microsoft Academic Search

Ion implantation is a useful method to incorporate dopants into semiconductors. Understanding implantation processes is essential to the advancement of solid state technology. Because of its technical importance, gallium arsenide (GaAs) was chosen for this study. Hall effect, x-ray diffraction, and electrochemical capacitance-voltage (CV) profiling were used to study activation of silicon implants as functions of dose and annealing temperature

John Hamilton Madok

1993-01-01

86

Hepatocellular carcinoma detection by gallium scan and subsequent treatment by gallium maltolate: rationale and case study.  

PubMed

Gallium is antiproliferative to many types of cancer, due primarily to its ability to act as a non-functional mimic of ferric iron (Fe(3+)). Because Fe(3+) is needed for ribonucleotide reductase activity--and thus DNA synthesis--gallium can inhibit DNA production and cell division. Diagnostic gallium scans have shown that hepatocellular carcinoma (HCC) is commonly avid for gallium. Furthermore, in vitro studies have found that gallium nitrate, and particularly gallium maltolate (GaM), have dose-dependent antiproliferative activity against HCC cell lines. Rationale thus exists to use GaM, an orally active compound that has been well tolerated in Phase I clinical trials, to treat patients whose HCC is gallium-avid in a gallium scan. Because gallium absorbed from orally administered GaM is bound predominately to serum transferrin, which travels to all tissues in the body, GaM has the potential to treat even distant metastases. A patient with advanced HCC (20 × 10 cm primary tumor, ascites around liver and spleen, resistant to Nexavar(®) (sorafenib)), whose cancer was highly gallium-avid in a (67)Ga-scan, was treated with oral gallium maltolate at 1500 mg/day q.d. After four weeks of treatment, the patient had a large reduction in pain, with greatly increased mobility and quality of life, and significantly lowered serum bilirubin and inflammation-related liver enzymes. At eight weeks, CT scans showed apparent necrosis of the tumor. PMID:21554205

Bernstein, Lawrence R; van der Hoeven, Jacobus J M; Boer, Robbert O

2011-07-01

87

Laser Photochemistry of Gallium-Containing Compounds.  

National Technical Information Service (NTIS)

The production of gas-phase gallium atoms in the photolysis of trimethylgallium has been investigated at 193 nm and at other laser wavelengths. Ground state (4 sup 2 P sup 0 /sub 1/2) and metastable (4 sup 2 P sup 0 /sub 3/2/) gallium atoms are detected u...

S. L. Baughcum R. C. Oldenborg

1986-01-01

88

Optical control of gallium nanoparticle growth  

NASA Astrophysics Data System (ADS)

We report that low-intensity light can dramatically influence and regulate the nanoparticle self-assembly process: Illumination of a substrate exposed to a beam of gallium atoms results in the formation of gallium nanoparticles with a relatively narrow size distribution. Very low light intensities, below the threshold for thermally induced evaporation, exert considerable control over nanoparticle formation.

MacDonald, K. F.; Fedotov, V. A.; Pochon, S.; Ross, K. J.; Stevens, G. C.; Zheludev, N. I.; Brocklesby, W. S.; Emel'Yanov, V. I.

2002-03-01

89

Large grain gallium arsenide thin films  

SciTech Connect

Polycrystalline gallium arsenide films deposited on tungsten/graphite substrates have been used for the fabrication of thin film solar cells. Gallium arsenide films deposited on foreign substrates of 10 ..mu..m or less thickness exhibit, in most cases, pronounced shunting effects due to grain boundaries. MOS solar cells of 9 cm/sup 2/ area with an AMI efficiency of 8.5% and p/sup +//n/n/sup +/ homojunction solar cells of 1 cm/sup 2/ area with an AM1 efficiency of 8.8% have been prepared. However, in order to further improve the conversion efficiency before the development of effective passivation techniques, gallium arsenide films with large and uniform grain structure are necessary. The large grain gallium arsenide films have been prepared by using the arsine treatment of a thin layer of molten gallium on the substrate surface and the recrystallized germanium films on tungsten/graphite as substrates.

Chu, S.S.; Chen, W.J.; Chu, T.L.; Firouzi, H.; Han, Y.X.; Wang, Q.H.

1984-05-01

90

Triethylborane-induced radical reactions with gallium- and indium hydrides  

Microsoft Academic Search

A gallium hydride reagent, HGaCl2, was found to act as a radical mediator. Treatment of alkyl halides with the gallium hydride reagent, generated from gallium trichloride and sodium bis(2-methoxyethoxy)aluminum hydride, provided the corresponding reduced products in excellent yields. Radical cyclization of halo acetals was also successful with not only the stoichiometric gallium reagent but also a catalytic amount of gallium

Kazuaki Takami; Satoshi Mikami; Hideki Yorimitsu; Hiroshi Shinokubo; Koichiro Oshima

2003-01-01

91

Plutonium Alloys Containing Controlled Amounts of Plutonium Allotropes Obtained by Application of High Pressures.  

National Technical Information Service (NTIS)

The alloys are useful as nuclear fission reactor fuels in the form of solid rods or other shapes. A stabilized plutonium base alloy containing from 0.6 to 4.0 atom percent gallium aluminum, or zinc is made by compressing the alloy to its transformation pr...

R. O. Elliott K. A. Gschneidner

1964-01-01

92

Electrospun Gallium Nitride Nanofibers (abstract)  

NASA Astrophysics Data System (ADS)

The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH3 flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

2009-04-01

93

The Soviet American Gallium Experiment (SAGE)  

SciTech Connect

A radiochemical experiment using the reaction v/sub e/ = /sup 71/Ga + e/sup e/ to determine the integral flux of low-energy neutrinos from the sun is currently under preparation at the Baksan Neutrino Observatory in the USSR. Measurements are scheduled to commence by late 1988 using /approximately/30 tonnes of metallic gallium. With this amount of gallium it should be possible to obtain a fractional statistical accuracy of 12 to 15% after one year (assuming the standard solar model neutrino flux). While initial measurements are in progress, installation of the remaining 30 tonnes of gallium will proceed in order to perform the full 60 tonne experiment.

Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.P.; Avdeyev, A.V.; Belousko, Yu.I.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Gavrin, V.N.; Grigorjev, A.M.; Kalikhov, A.V.; Kireyev, S.M.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentsevah, S.A.; Mirnov, I.N.; Ejikbosverpdze, Sh.M.; Ostrinsky, A.V.; Petukhov, V.V.; Pikhulya, O.E.; Pshukov, A.M.; Revzin, N.Ye.; Shikhin, A.A.; Shilo, Yu.I.; Slyusareva, Ye.D.; Strepanyuk, M.V.; Tikhonov, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Yants, V.E.; Zakhorov, Yu.I.; Zatsepin, G.T.; Cleveland, B.C.; Bowles, T.J.; Elliott, S.R.; O'Brien, H.A.; Wark, D.L.; Wilkerson, J.F.; Cherry, M.L.; Kouzes, R.T.

1988-01-01

94

Status of gallium-67 in tumor detector  

SciTech Connect

The efficacy of gallium-67 citrate in detecting specific tumors is discussed. Tumors in which gallium-67 imaging is useful as a diagnostic tool include Hodgkin's disease, histiocystic lymphoma, Burkitt's lymphoma, hepatoma melanoma, and leukemia. It has not been found to be effective in diagnosing head and neck tumors, gastrointestinal tumors, genitourinary tract tumors, breast tumors, and pediatric tumors. Gallium may be useful in the evaluation of non-Hodgkin's lymphoma, testicular carcinoma, mesothelioma, and carcinoma of the lung. It may also be useful for determining response to treatment and prognosis in some neoplasms.

Hoffer, P.

1980-04-01

95

Recovery of gallium from aluminum industry residues  

SciTech Connect

A procedure is proposed to recover gallium from flue dust aluminum residues produced in plants by using solid-phase extraction with a commercial polyether-type polyurethane foam (PUF). Gallium can be separated from high concentrations of aluminum, iron, nickel, titanium, vanadium, copper, zinc, sulfate, fluoride, and chloride by extraction with PUF from 3 M sulfuric acid and 3 M sodium chloride concentration medium with at least a 92% efficiency. Gallium backextraction was fast and quantitative with ethanol solution. In all recovery steps commercial-grade reagents could be used, including tap water. The recovered gallium was precipitated with sodium hydroxide solution, purified by dissolution and precipitation, calcinated, and the final oxide was 98.6% pure.

Carvalho, M.S.; Neto, K.C.M.; Nobrega, A.W.; Medeiros, J.A.

2000-01-01

96

Generator for gallium-68 and compositions obtained therefrom  

DOEpatents

A generator for obtaining radioactive gallium-68 from germanium-68 bound in a resin containing unsubstituted phenolic hydroxyl groups. The germanium-68 is loaded into the resin from an aqueous solution of the germanium-68. A physiologically acceptable solution of gallium-68 having an activity of 0.1 to 50 millicuries per milliliter of gallium-68 solution is obtained. The solution is obtained from the bound germanium-68 which forms gallium-68 in situ by eluting the column with a hydrochloric acid solution to form an acidic solution of gallium-68. The acidic solution of gallium-68 can be neutralized.

Neirinckx, Rudi D. (Medfield, MA); Davis, Michael A. (Westwood, MA)

1981-01-01

97

Aluminum arsenide eutectic gallium arsenide solar cell  

Microsoft Academic Search

An improved gallium arsenide solar cell is provided by forming a P+ layer on top of a wafer of vertical PN junction eutectic gallium arsenide crystal by liquid phase epitaxial growth of P doped GaAs followed by liquid phase epitaxial growth at Al(x)AsGa(1-x) on the surface of the vertical PN junction substrate. The deposited GaAs layer with P dopant and

Rahilly

1976-01-01

98

Aluminum arsenide eutectic gallium arsenide solar cell  

Microsoft Academic Search

An improved gallium arsenide solar cell is provided by forming a P + layer on top of a wafer of plural vertical PN junction eutectic gallium arsenide crystal by liquid phase epitaxial growth of P doped GaAs followed by liquid phase epitaxial growth at Al\\/sub x\\/AsGa\\/sub l-x\\/ on the surface of the vertical PN junction substrate. The deposited GaAs layer

Rahilly

1978-01-01

99

Nanoscale photonics of structural transformations in Gallium  

NASA Astrophysics Data System (ADS)

We have found recently that Gallium, confined at an interface with silica, responds dramatically to low power optical excitation when held at temperatures close to its melting point (29.8°C). Intensities of just a few kW/cm2 can reversibly modulate the intensity (by up to 40%) and phase (by as much as several degrees) of reflected light as the result of a light-induced structural transition occurring in a layer of gallium of only a few nm thick. Here, we report that this concept - of achieving a nonlinearity via a light-induced transformation in a confined solid at a temperature close to a phase transition temperature - can also be applied to gallium nanoparticles. We present the transient all-optical switching characteristics of gallium nanoparticle films comprising particles, typically 80 nm in diameter, which were formed directly on the ends of optical fibers using a new light-assisted self-assembly technique. We also report, for the first time, that this light-induced structural transition in gallium confined at an interface with silica underlies a new mechanism for photoconductivity. In our opinion, the exploitation of the light-induced phase transition in gallium may be a means of enabling the development of nanoscale photonic devices.

Zheludev, Nikolay I.; Fedotov, V. A.; MacDonald, K. F.; Stevens, G. C.; Pochon, Sebastien C.; Woodford, M.

2002-09-01

100

The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal  

SciTech Connect

Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH{sub 2}). The heats of solution for PuH{sub s} and PuD{sub s} are determined from PCT data in the ranges 350-625 C for gallium alloyed Pu and 400-575 C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

Richmond, Scott [Los Alamos National Laboratory; Bridgewater, Jon S [Los Alamos National Laboratory; Ward, John W [Los Alamos National Laboratory; Allen, Thomas A [Los Alamos National Laboratory

2009-01-01

101

The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal  

NASA Astrophysics Data System (ADS)

Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH2). The heats of solution for PuHS and PuDS are determined from PCT data in the ranges 350-625°C for gallium alloyed Pu and 400-575°C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

Richmond, S.; Bridgewater, J. S.; Ward, J. W.; Allen, T. H.

2010-03-01

102

Method of Fabricating Germanium and Gallium Arsenide Devices.  

National Technical Information Service (NTIS)

A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium...

M. Jhabvala

1990-01-01

103

Investigation of the thermal properties of gallium nitride using the three omega technique  

NASA Astrophysics Data System (ADS)

Gallium nitride based devices suffer from undesirable heating effects that significantly limit the performance of high electron mobility transistors and laser diodes thereby reducing device lifetime and reliability. An accurate knowledge of the gallium nitride thermal conductivity is crucial to understanding thermal effects. This work addresses issues related to both the thermal limitations and thermal characterization of gallium nitride alloys and devices. First, theoretical developments concerning the three omega technique applied to a film-on-substrate system are considered when the film-to-substrate thermal conductivity ratio is larger than one. The case of thermal boundary resistance between film and substrate is included. In the case of high thermal conductivity films, it is found that neglecting the presence of thin thermally insulating buffer layer would lead to large uncertainties in extracted film thermal conductivities. Next, very thick, free standing gallium nitride layers grown by hydride vapor phase epitaxy were precisely measured from 300K to 450K using the three omega method. By comparing the measured values with dislocation density measurements the dependence of the gallium nitride thermal conductivity on dislocation density was obtained and compared with theory. In addition, the thermal conductivity of iron doped semi-insulating gallium nitride was measured to be as high as 230 W·K-1·m-1. In this study, a 2mm thick iron doped gallium nitride substrate was measured to have an average dislocation density of 5.104 cm-2 which represents the present state of the art. Finally the modeling of the thermal resistance of multifinger AlGaN/GaN HEMTs was examined using the experimentally determined values of the thermal conductivity. Using the three omega method as the starting point, an original accurate closed-form compact expression for the thermal resistance of single and multifinger HEMT device structures was derived. It was found that the thermal performance of a single finger HEMT composed of homoepitaxial GaN on a GaN substrate is superior to that of single finger GaN HEMT heteroepitaxially grown on silicon carbide.

Mion, Christian

104

The nature of subvalent gallium and indium in aqueous media  

Microsoft Academic Search

Subvalent gallium can exist in aqueous solutions as Ga?Ga bonded gallium(II) species stabilised by halide ligands in the form of the complex anions Ga2X62? (X=Cl, Br or I) whose formation and reactivity are discussed. Gallium(I) compounds and mixed valence compounds of gallium react vigorously with water, converting any Ga+ ions into Ga(III) products. Indium(I) is more tolerant of water, so

Lars Kloo; Jan Rosdahl; Michael J. Taylor

2002-01-01

105

Studies of the Vaporization Mechanism of Gallium Arsenide Single Crystals  

Microsoft Academic Search

The kinetics of vaporization of gallium arsenide single crystals into vacuum have been investigated using microbalance and mass spectrometric techniques in the temperature range 700–900° C. Although gallium arsenide vaporized incongruently to yield liquid gallium and arsenic vapor molecules, initial steady state evaporation rates can be obtained in the temperature range of study. The total evaporation rates and the activation

C. Y. Lou; G. A. Somorjai

1971-01-01

106

Proportional counter response calculations for gallium solar neutrino detectors  

Microsoft Academic Search

Gallium-based solar neutrino detectors are sensitive to the primary pp reaction in the sun. Two experiments using gallium, SAGE in the Soviet Union and GALLEX in Europe, are under construction and are scheduled to produce data by 1989. The radioactive 71Ge produced by neutrinos interacting with the gallium detector material is chemically extracted and counted in miniature proportional counters. A

R. T. Kouzes; D. Reynolds

1989-01-01

107

Gallium Concentrations in the Metal Phases of Various Meteorites  

Microsoft Academic Search

The metal phases of seven chondrites and fourteen iron meteorites have been analyzed for gallium by neutron activation. Gallium is quite uniform in the ordinary H- and L-group chondrites and averages 12 ppm. The metal phase of the Abee enstatite chondrite contains 64 ppm Ga. It has previously been established that gallium abundances in iron neteorites are distributed around certain

James C. Cobb; George Moran

1965-01-01

108

Gallium Zeolites for Light Paraffin Aromatization  

SciTech Connect

The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

Price, G.L.; Dooley, K.M.

1999-02-10

109

Production of gallium atoms by excimer laser photolysis of trimethyl gallium  

SciTech Connect

The gas phase kinetics of group III elements such as gallium are important in possible chemically driven energy transfer lasers and in chemical vapor deposition processes in the electronics industry. Excimer laser photodissociation of volatile gallium compounds via multiple photon process provides, in principle, a convenient room temperature source of gallium atoms for study using laser photolysis-laser induced fluorescence techniques. In this paper, we report preliminary results of the multiple photon dissociation of trimethyl gallium at 193 nm. Prompt emission from a number of excited gallium states (5 /sup 2/S, 4 /sup 2/D, 6 /sup 2/S, 6 /sup 2/P/sup 0/, 5 /sup 2/D, and 4 /sup 4/P) has been observed. The time histories of the ground state (4/sup 2/P/sup 0//sub 1/2/) and the metastable (4 /sup 2/P/sup 0//sub 3/2/) have been measured using laser induced fluorescence. The resulting time profiles are complicated even in the absence of a reactant gas by the apparent production of ground state gallium at relatively long times (approx. 10 ..mu..s) after the excimer laser pulse. Possible mechanisms for this (i.e., radical reactions to produce gallium, energy transfer cascading from high lying metastable states, ionic processes, etc.) are being investigated. These results indicate that the photodissociation of trimethyl gallium at 193 nm is complex. Photolysis studies at other wavelengths and with other precursors are in progress to find a cleaner source of gas phase atomic gallium for kinetic studies. 20 refs., 7 figs.

Baughcum, S.L.; Oldenborg, R.C.; Winn, K.R.; Hof, D.E.

1985-03-01

110

Effects of titanium-dental restorative alloy galvanic couples on cultured cells.  

PubMed

The potential exists for titanium and amalgams to become galvanically coupled in the oral cavity. While low galvanic corrosion rates have been measured in vivo for titanium-amalgam or mercury-free alloy couples, concerns exist over released corrosion products and adverse tissue responses. It was hypothesized in this study that coupling titanium to amalgams or gallium alloys increased the release of metallic corrosion products and decreased cellular activity and function. The effects of titanium coupled and uncoupled to a conventional amalgam, palladium-enriched spherical high copper amalgam, a dispersed type high copper amalgam, and a mercury-free gallium alloy were evaluated in 24-h cell culture tests. Viability, proliferation, and collagen synthesis were evaluated by the uptake of neutral red, 3H-thymidine, and immunoassay of procollagen, respectively, and compared to cells not exposed to any test material. The gallium alloy-titanium couple resulted in significant decreases in cellular viability, proliferation, and collagen synthesis as compared to the other coupled and uncoupled samples. Few differences in the cellular responses of the other coupled and uncoupled samples were observed. Atomic absorption analyses indicated increased release of metal ions from the amalgam and gallium alloy samples coupled to titanium as compared to their uncoupled condition, although the differences were not always significant. Galvanic corrosion of amalgam-titanium couples in the long term may become significant, and further research is needed. Coupling the gallium alloy to titanium may result in increased galvanic corrosion and cytotoxic responses. PMID:9619437

Bumgardner, J D; Johansson, B I

1998-01-01

111

Surface passivation of Gallium Arsenide  

NASA Astrophysics Data System (ADS)

The surface passivation of Si doped (100) n-type gallium arsenide (GaAs) by chemical treatment with phosphoric acid (H3P04), phosphorus trichloride (PCl3), and sodium sulfide (Na2S.9H2O) was investigated using room temperature photoluminescence (PL) and a capacitance-voltage (C-V) and current-voltage (I-V) profiler. After passivation, the 300K PL increased for all three treatments. Best results obtained showed improvements of 1.4, 3.5 and 5.3 times greater of PL efficiency for H3PO4, PCl3 and Na2S, respectively, over unpassivated samples that were only cleaned and etched. Samples that were cleaned, etched and washed with de-ionized 18 Mohm, 5 ppm O2 content water showed about the same PL increase as the H3PO4 passivation. Capacitance-voltage and I-V profile curves showed the removal of the surface oxide hysteresis with the PCl3 passivated samples; however, re-oxidation seems to take longer than normal and to be confined to the passivation layer.

Racicot, Robert J.

1988-04-01

112

/sup 67/Gallium lung scans in progressive systemic sclerosis  

SciTech Connect

/sup 67/Gallium lung scans were performed in 19 patients with progressive systemic sclerosis (scleroderma). Results were expressed quantitatively as the /sup 67/Gallium Uptake Index. The mean total pulmonary /sup 67/Gallium Uptake Index in patients was significantly higher than that in controls (41 versus 25), and 4 patients (21%) fell outside the normal range. There were no clinical or laboratory variables that correlated with the /sup 56/Gallium uptake. Increased pulmonary /sup 67/Gallium uptake in scleroderma may prove useful as an index of pulmonary disease activity.

Baron, M.; Feiglin, D.; Hyland, R.; Urowitz, M.B.; Shiff, B.

1983-08-01

113

New SMU Gallium Fixed-Point Cells  

NASA Astrophysics Data System (ADS)

In the framework of the European research project EURAMET 732, the Slovak Institute of Metrology (SMU) built three primary gallium fixed-point cells of different designs. The cells are designed for the calibration of the long-stem SPRT. In regard to the procedure commonly used at SMU when realizing the gallium point, the cells are designed for use in a stirred liquid bath. This article provides information about the cell designs, materials used, method of filling, and results of the performed experiments. The experiments were focused on the study of the cells' metrological characteristics, some effects that could influence the melting-point temperature and the effect of the melted metal fraction on the immersion profile. New cells were compared with the SMU reference gallium cell.

Ranostaj, Juraj; ?uriš, Stanislav; Knorová, Renáta; Kaskötö, Mariana; Vysko?ilová, Irena

2011-08-01

114

The wetting of alumina by copper alloyed with titanium and other elements  

Microsoft Academic Search

The wettability of alumina by ternary alloys of copper, titanium and aluminium, gallium gold, indium, nickel or silver has been investigated using sessile drop tests conducted in vacuum at 1050–1250° C. Substantial additions of titanium are known to induce copper to wet alumina due to the formation of a titanium rich reaction product at the alloy\\/ ceramic interface, but the

M. G. Nicholas; T. M. Valentine; M. J. Waite

1980-01-01

115

Distribution Coefficient of Germanium in Gallium Arsenide Crystals Grown from Gallium Solutions  

Microsoft Academic Search

Gallium arsenide crystals doped with germanium were grown from gallium solutions at 900°–875°C. The Ge concentration in the liquid was varied from 0.004 to 56 at.%, and the Ge concentration in the GaAs crystals determined using radiotracer and other techniques. The Ge concentration in the solid varied linearly with increasing Ge concentration in the liquid up to 5 at.% and

F. E. Rosztoczy; K. B. Wolfstirn

1971-01-01

116

Foundations of ohmic contact formation on aluminum gallium nitride\\/gallium nitride heterostructures  

Microsoft Academic Search

Aluminum gallium nitride (AlGaN)\\/gallium nitride (GaN) high electron mobility transistors (HEMTs) have tremendous potential for application in high frequencies, high temperatures and microwave and mm power amplifications. Fabrication of Ohmic contacts for such devices that meet the stringent low-resistance, high thermal stability and smooth surface morphology requirements has been challenging. In the cases where Ohmic behavior can be achieved, a

Fitih Mustefa Mohammed

2007-01-01

117

Synchrotron X-Ray Fluorescence Microscopy of Gallium in Bladder Tissue following Gallium Maltolate Administration during Urinary Tract Infection.  

PubMed

A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 ?g/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli. PMID:23877680

Ball, Katherine R; Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L; Blyth, Robert I R; Sham, Tsun-Kong; Dowling, Patricia M; Thompson, Julie

2013-07-22

118

Ultraviolet Photoelectron Spectra of Gallium Arsenide Clusters.  

National Technical Information Service (NTIS)

The ultraviolet photoelectron spectra (UPS) of mass-selected negative gallium arsenide cluster ions in the 2-50 atom size range was measured with a photon energy of 7.9 eV. The measured photodetachment thresholds displayed a strong even/odd oscillation th...

C. Jin J. Conceicao K. J. Taylor R. E. Smalley

1990-01-01

119

Interfacing epitaxial oxides to gallium nitride  

Microsoft Academic Search

Molecular beam epitaxy (MBE) is lauded for its ability to control thin film material structures at the atomic level. This precision of control can improve performance of microelectronic devices and cultivate the development of novel device structures. This thesis explores the utility of MBE for designing interfaces between oxide epilayers and the wide band gap semiconductor gallium nitride (GaN). The

Mark Daniel Losego

2008-01-01

120

SPECT gallium imaging in abdominal lymphoma  

SciTech Connect

A case of non-Hodgkin's lymphoma of the abdomen studied by gallium SPECT imaging is reported. The tomographic slices accurately demonstrated the location of residual disease after chemotherapy in the region of the transverse mesocolon. Previous transmission CT had shown considerable persistent retroperitoneal lymphadenopathy, but was not helpful in determining the presence of viable lymphoma.

Adcock, K.A.; Friefeld, G.D.; Waldron, J.A. Jr.

1986-05-01

121

Photoluminescence Study of Germanium Implanted Gallium Arsenide.  

National Technical Information Service (NTIS)

The low temperature photoluminescence properties of Ge implanted Gallium Arsenide has been analyzed. Samples were singly implanted with Ge and As, and with Ge and Ga. The substrate used was semi-insulating Chromium-doped GaAs. All ions were implanted at r...

B. P. Thoma

1985-01-01

122

Producing gallium arsenide crystals in space  

Microsoft Academic Search

The production of high quality crystals in space is a promising near-term application of microgravity processing. Gallium arsenide is the selected material for initial commercial production because of its inherent superior electronic properties, wide range of market applications, and broad base of on-going device development effort. Plausible product prices can absorb the high cost of space transportation for the initial

R. L. Randolph

1984-01-01

123

High efficiency monolithic gallium nitride distributed amplifier  

Microsoft Academic Search

The first gallium-nitride monolithic distributed amplifier is demonstrated. A nonuniform design allows the removal of the drain line dummy load with a concomitant increase in efficiency, An optimized nonuniform design shows a 10% increase in efficiency over an optimized uniform design having the dummy termination

Bruce M. Green; Sungjae Lee; Kenneth Chu; Kevin J. Webb; Lester F. Eastman

2000-01-01

124

The Influence of Lewis Acid/Base Chemistry on the Removal of Gallium by Volatility from Weapons-Grade Plutonium Dissolved in Molten Chlorides  

SciTech Connect

It has been proposed that GaCl{sub 3} can be removed by direct volatilization from a Pu-Ga alloy that is dissolved in a molten chloride salt. Although pure GaCl{sub 3} is quite volatile (boiling point: 201 deg. C), the behavior of GaCl{sub 3} dissolved in chloride salts is quite different because of solution effects and is critically dependent upon the composition of the solvent salt (i.e., its Lewis acid/base character). In this technical note, the behavior of gallium in prototypical Lewis acid and Lewis base salts is contrasted. It is found that gallium volatility is suppressed in basic melts and promoted in acidic melts. These results have an important influence on the potential for simple gallium removal in molten salt systems.

Williams, David F.; Cul, Guillermo D. del [Oak Ridge National Laboratory (United States); Toth, Louis M. [Electrochemical Systems (United States); Collins, Emory D. [Oak Ridge National Laboratory (United States)

2001-12-15

125

Dose dependent disposition of gallium-67 in rats  

SciTech Connect

Radioactive gallium-67 has been employed as a diagnostic and follow-up agent for cancer therapy. Currently gallium nitrate is undergoing Phase I clinical studies. A million fold increase in the concentration of the carrier gallium citrate over the range of carrier-free gallium-67 (pgm) to 1.0 ..mu..g caused no significant alteration in the disposition of gallium-67 in rats.Gallium-67 was eliminated from blood with a biological t1/2 of 4.1 days. A linear tissue binding profile was observed for gallium-67 over this concentration range. A multi-compartment pharmacokinetic model was developed in which all the tissues studied were treated as separate compartments. At 1.0 mg dose level, significant alteration in the disposition of gallium-67 was observed in rats, > 95% of the initial radioactivity was characteristic reappearance of the radioactivity in the blood approximately 4 hours after dosing leading to a ''hump'' in the blood concentration-time profiles. Following the 1.0 mg dose low tissue levels were observed, except for the kidneys, which contained about 8% of the administered dose per gram of the tissue one-half hour after dosing. A non-linear tissue binding profile was observed to be associated with gallium at high doses. It was hypothesized that the rapid loss of gallium-67 from the vascular system following the high doses of gallium citrate was due to the accumulation of the drug in the kidneys where it was eventually eliminated via urine. The kidneys thus would act as a temporary storage site for gallium. It was concluded that the dose-related renal toxicity associated with gallium therapy may be attributed to the kidney's role as a temporary storage site following high doses.

Gautam, S.R.

1982-01-01

126

40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.  

Code of Federal Regulations, 2010 CFR

...Description of the primary and secondary germanium and gallium subcategory. 421.180...SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180...Description of the primary and secondary germanium and gallium subcategory. The...

2009-07-01

127

40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.  

Code of Federal Regulations, 2010 CFR

...Description of the primary and secondary germanium and gallium subcategory. 421.180...SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180...Description of the primary and secondary germanium and gallium subcategory. The...

2010-07-01

128

Gallium 67 scintigraphy in glomerular disease  

SciTech Connect

To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

1988-12-01

129

Gallium nitride nanowire electromechanical resonators  

NASA Astrophysics Data System (ADS)

Nanoscale mechanical resonators are of great interest for high-resolution sensing applications, where the small resonator mass and high quality factor (Q, defined as resonance frequency f0 over full width at half maximum power) lead to unprecedented sensitivity. Here, we investigate gallium nitride (GaN) nanowire (NW) resonators. The single-crystal, c-axis NWs are 5 mum -- 20 mum long, with diameters from 50 nm -- 500 nm, and grow essentially free of defects. Our initial experiments involve measuring the resonances of as-grown NWs in a scanning electron microscope, where we observe exceptionally high Q values of 10 4 -- 105, one to two orders of magnitude higher than most NWs of comparable size. Using a single NW as a mass sensor, we then demonstrate a sub-attogram mass sensitivity. To provide a more flexible measurement technique that avoids electron-microscope detection, we fabricate doubly clamped NWs with an entirely electronic drive and readout scheme using a combination of lithographic patterning and dielectrophoresis. An electrostatic gate induces vibration, while readout utilizes the piezoresistivity of GaN. Observed resonances range from 9--36 MHz with Q values typically around 103 at room temperature and 10 -4 Pa. We use the behavior of f0 and Q to sense the NW's local environment, such as the additional sources of energy dissipation not present in the as-grown NWs. By cooling the device to 8 K, Q increases by an order of magnitude to above 104, with a highest value to date of 26,000 under vacuum. We explore additional NW properties through the thermal noise in the NW's mechanical motion and the exponential decay of mechanical motion in the presence of burst drive. Finally, we investigate the low-frequency 1/f parameter noise displayed by f0. We show that the noise in f0 is consistent with noise in the NW's resistance leading to temperature noise from local Joule heating, which in turn generates resonance frequency noise. For sensor applications, there will be optimal drive conditions that balance the f 0 noise with the signal-to-noise ratio of the system. With these insights, along with the simple drive and readout technique, these GaN-NW doubly clamped resonators have significant potential for high-resolution sensing applications.

Gray, Jason Michael

130

Mechanism of Intergranular Penetration of Ga in an Aluminum Alloy  

Microsoft Academic Search

The intergranular penetration rates of gallium in 7050-T74 aluminum alloy were examined at temperatures from 25C to 180C under stress free condition. The results provide an estimate of activation energy of the penetration process. The penetration of Ga is observed to occur along the grain boundary and also spread over the surface, but much more slowly. Experiments were also performed

Boxiong Ding; Richard Hoagland

1998-01-01

131

Beryllium diffusion properties in dilute nitride alloys of gallium arsenide  

NASA Astrophysics Data System (ADS)

III-V dilute nitrogen materials (GaAsN and GaInNAs) are excellent candidates for long wavelength optoelectronic applications, including Lasers, HBTs and solar cells. The research of diffusion phenomenon and mechanism in these materials is an important topic for both research and manufacturing. The objective of this study was to investigate and discuss Be diffusion behavior and its mechanism in lightly and dilute N doped GaAs by chemical beam epitaxy (CBE) growth. The diffusivity and activation energy with nitrogen composition of 0.01% and 2% incorporation by radio frequency (RF) nitrogen plasma assisted chemical beam epitaxial growth of GaAs are reported here for the first time. The SIMS and ECV profiles of as-grown and annealed samples are investigated to provide a theoretical fit to compare the feature of diffusion behavior on both samples of different N doping content. Furthermore, we discuss interaction of charged point defects and the effect of N and H doping on Be diffusion. There is also an attempt to explain the experimental results with a diffusion mechanism. It may have a profound impact on the design and fabrication process of dilute nitride based devices.

Zhu, Wenkai

132

Gallium arsenide infrared windows for high-speed airborne applications  

NASA Astrophysics Data System (ADS)

Large (7- by 16-inch) plates of semi-insulating gallium arsenide suitable for use as external infrared transmitting windows were grown using a unique compounding process. The plates were grown in an open tube system, the gallium arsenide being solidified from a stoichiometric melt. Detailed growth conditions are discussed. The optical and physical properties of this material are compared with other candidate infrared (IR) optical materials. In addition, some results of captive flight tests comparing gallium arsenide with germanium are given

Brau, M. J.; Stone, L. E.; Boucher, M. W.

1982-10-01

133

Field emission from gallium-doped zinc oxide nanofiber array  

Microsoft Academic Search

Gallium-doped nanostructural zinc oxide fibers have been fabricated by vapor-phase transport method of heating the mixture of zinc oxide, gallium oxide, and graphite powders in air. The zinc oxide fibers grew along [002] direction, forming a vertically aligned array that is predominantly perpendicular to the substrate surface. With a gallium doping concentration of 0.73 at. %, the corresponding carrier concentration

C. X. Xu; X. W. Sun; B. J. Chen

2004-01-01

134

Gallium scintigraphy in the detection of amiodarone lung toxicity  

SciTech Connect

Fourteen gallium scans were obtained in 11 patients suspected of having amiodarone lung toxicity on the basis of clinical findings, pulmonary function tests, and chest radiographs. All 11 patients had abnormal scans. Gallium accumulates in various inflammatory and neoplastic lesions, but despite this nonspecificity, the findings suggest gallium scintigraphy is a useful procedure to detect amiodarone lung toxicity when used in the appropriate clinical setting.

Moinuddin, M.; Rockett, J.

1986-09-01

135

Interactions of zircaloy cladding with gallium -- 1997 status  

SciTech Connect

A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance of prototypic Zircaloy cladding materials against: (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge} 300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

Wilson, D.F.; DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.

1997-11-01

136

Interactions of Zircaloy cladding with gallium: 1998 midyear status  

SciTech Connect

A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge}300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

1998-06-01

137

Ultrafast physics in microstructure and alloy systems  

NASA Astrophysics Data System (ADS)

During year one of AFOSR 860031, significant progress has been achieved in: (1) the main thrust area of ultrafast physics in microstructures and alloys semiconductors - regarding carrier dynamics using picosecond photoluminescence kinetics of 2D Gallium Arsenide/Gallium Aluminum Arsenide (QW) on 2 to 50 pico second time scale; dependence of electron temperature on well width in single Aluminum Indium Galide/Galium Indium Arsenide QW; determination of valence band discontinuity via optical transitions in ultrathin QW; high density electron-hole plasma energy relaxation and rapid expansion; ultrafast carrier recombination relaxation in magnetic semiconductor; and emission and relaxation dynamics in optical deformation semiconductor Cadmium Sulfur Selenide alloy glasses; and in (2) ultrafast pulse propagation in dielectrics and semiconductors - regarding the observation of induced spectral broadening in Zinc Selenide and BK-7 glass.

Alfano, Robert

1987-02-01

138

Corrosion development between liquid gallium and four typical metal substrates used in chip cooling device  

NASA Astrophysics Data System (ADS)

The limitation of the currently available thermal management method has put an ever serious challenge for computer chip designers. A liquid metal with low melting point around room temperature was recently identified as a powerful coolant of driving heat away because of its superior thermo-physical properties and the unique ability to be driven efficiently by a completely silent electromagnetic pump. However, the adoption of gallium, one of the best candidates as metal coolant so far, may cause serious corrosion to the structure materials and subsequently affect the performance or even dangerous running of the cooling system. To address this emerging critical issue, here the compatibility of gallium with four typical metal substrates (6063 Aluminum-Alloy, T2 Copper-Alloy, Anodic Coloring 6063 Aluminum-Alloy and 1Cr18Ni9 Stainless Steel) was comprehensively investigated in order to better understand the corrosion mechanisms and help find out the most suitable structure material for making a liquid metal cooling device. To grasp in detail the dynamic corrosion behavior, an image acquisition and contrasting method was developed. Moreover, corrosion morphology analyses were performed by means of scanning electron microscope (SEM). The chemical compositions of the corroded layers were evaluated using energy dispersive spectrometry (EDS). According to the experiments, it was found that, the corrosion of the 6063 Aluminum-Alloy was rather evident and serious under the temperature range for chip cooling. The loose corrosion product will not only have no protection for the inner substrate, but also accelerate the corrosion process. Compared to the 6063 Aluminum-Alloy, T2 Copper-Alloy showed a slow and general corrosion, but part of the corrosion product can shed from the substrate, which will accelerate corrosion action and may block the flowing channel. Anodic Coloring 6063 Aluminum-Alloy and 1Cr18Ni9 Stainless Steel were found to have excellent corrosion resistance among these four specimens. No evident corrosion phenomena were found under the examination of SEM and EDS when exposed for 30 days at the temperature of 60°C, which suggests their suitability as structure materials for the flow of liquid metal. However, as for the Anodic Coloring 6063 Aluminum-Alloy, surface treatment and protection are of vital importance. The present study is of significance for making a liquid metal chip cooling device which can actually be used in the future computer industry.

Deng, Yue-Guang; Liu, Jing

2009-06-01

139

Gallium-67 imaging in muscular sarcoidosis  

SciTech Connect

A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

1984-07-01

140

IBIC analysis of gallium arsenide Schottky diodes  

Microsoft Academic Search

Semi-insulating (SI) gallium arsenide (GaAs) devices operating as a reverse biased Schottky diode offer an attractive choice as radiation detector at room temperature both in high energy physics experiments and as X-ray image sensors. However, SI GaAs devices contain a high concentration of traps, which decreases the charge collection efficiency (cce), and affects the energy resolution of such detectors working

E. Vittone; F Fizzotti; K Mirri; E Gargioni; P Polesello; A LoGiudice; C Manfredotti; S Galassini; P Rossi; P Vanni; F Nava

1999-01-01

141

Diffusion of iron in gallium selenide  

SciTech Connect

The temperature dependence of the diffusion coefficient of iron in gallium selenide with a defective sphalerite lattice was studied in the range 98-450 C. Iron 55 and Iron 59, in the form of an iron chloride solution, were used as tracers. The activation energies of fast and slow diffusion in alpha-Ga/sub 2/Se/sub 3/ were determined to be, respectively, 25.1 and 21.2 kJ/mole.

Firsova, L.P.

1987-02-01

142

A Gallium multiphase equation of state  

SciTech Connect

A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.

Crockett, Scott D [Los Alamos National Laboratory; Greeff, Carl [Los Alamos National Laboratory

2009-01-01

143

Gallium arsenide - Solar panel assembly technology  

Microsoft Academic Search

Gallium arsenide (GaAs) solar cell devices are maturing at 18 percent AM0 efficiencies for liquid phase epitaxy (LPE) technology, and efforts must be intensified placing necessary focus on the development of panel assembly techniques, and ultimately panel manufacturing methods capable of maintaining these high efficiencies for on-panel operation. Key problems and solutions are described which were experienced during the assembly

D. Zemmrich; N. Mardesich; B. Macfarlane; R. Loo

1984-01-01

144

Strongly Photonic Macroporous Gallium Phosphide Networks  

Microsoft Academic Search

A photo-assisted electrochemical etching technique to fabricate macropores in single-crystalline gallium phosphide (GaP) with variable porosity has been developed. Scanning electron microscopy and x-ray diffraction experiments confirm that the material consists of three-dimensional, interconnected ran- dom networks with pore sizes of about 150 nanometers. Optical transmission measurements demonstrate that the nonabsorbing disordered structures strongly scatter light. The photonic strength is

Frank J. P. Schuurmans; Jao van de Lagemaat

1999-01-01

145

The Baksan gallium solar neutrino experiment  

SciTech Connect

A radiochemical /sup 71/Ga-/sup 71/Ge experiment to determine the integral flux of neutrinos from the sun has been constructed at the Baksan Neutrino Observatory in the USSR. Measurements have begun with 30 tonnes of gallium. The experiment is being expanded with the addition of another 30 tonnes. The motivation, experimental procedures, and present status of this experiment are presented. 43 refs., 1 fig., 1 tab.

Gavrin, V.N.; Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Girin, S.V.

1989-01-01

146

Foreign atom thermodynamics in liquid gallium arsenide  

Microsoft Academic Search

Thermodynamic equilibrium in gallium arsenide crystal growth systems with the components Ga–As–C–B–N–Si–O has been analysed by using a Gibbs energy minimisation computer package. Emphasis is placed on graphical representations to describe the behaviour of C, B, Si and O in the crystal growth melt at 1513K. The various experimentally observed correlations between solute elements in the liquid and the encapsulant

W. A. Oates; H. Wenzl

1998-01-01

147

Gallium-67 radionuclide imaging in acute pyelonephritis  

SciTech Connect

The symptoms and clinical course of patients with acute pyelonephritis are variable; likewise, urinalysis, blood cultures, and excretory urography may be normal or equivocal. The ability of gallium-67 to accumulate in areas of active inflammation was useful in the diagnosis of acute pyelonephritis in 12 cases. A multiplane tomographic scanner was used for imaging four of these patients. Initial experience with this scanner is also discussed.

Mendez, G.; Morillo, G.; Alonso, M.; Isikoff, M.B.

1980-01-01

148

Gallium arsenide for devices and integrated circuits  

SciTech Connect

Gallium Arsenide has long been hailed as the material of the future and it is only in recent years that the technology associated with its growth and processing has matured to the point where IC production can be contemplated at the industrial level. This point has now been reached and the electronics industries in Europe, the USA and Japan are actively moving from research activities into product development using this and related material. The text is divided into 15 chapters: Gallium Arsenide: Physical and Transport Properties; Liquid phase and Vapour Phase Epitaxy of GaAs and Related Compounds; Expitaxial Growth and GaAs: MBE and MOCVD; Characterization of GaAs I: Electrical Techniques; Characterization of GaAsII: Ion Beam Analysis; Ion Implantation; Wet and Dry Processing GaAs; Microwave and Millimetre - Wave Diodes; GaAs Mesfet's and High Electron Mobility Transistors (HEMT); Optoelectronic Devices and Components; Gallium Arsenide Monolithic Microwave Integrated Circuits; GaAs Digital Integrated Circuits; III-V Semiconductors for Solar Cells.

Morgan, D.V.; Thomas, H.

1986-01-01

149

Interfacing epitaxial oxides to gallium nitride  

NASA Astrophysics Data System (ADS)

Molecular beam epitaxy (MBE) is lauded for its ability to control thin film material structures at the atomic level. This precision of control can improve performance of microelectronic devices and cultivate the development of novel device structures. This thesis explores the utility of MBE for designing interfaces between oxide epilayers and the wide band gap semiconductor gallium nitride (GaN). The allure of wide gap semiconductor microelectronics (like GaN, 3.4 eV) is their ability to operate at higher frequencies, higher powers, and higher temperatures than current semiconductor platforms. Heterostructures between ferroelectric oxides and GaN are also of interest for studying the interaction between GaN's fixed polarization and the ferroelectric's switchable polarization. Two major obstacles to successful integration of oxides with GaN are: (1) interfacial trap states; and (2) small electronic band offsets across the oxide/nitride interface due to the semiconductor's large band gap. For this thesis, epitaxial rocksalt oxide interfacial layers (˜8 eV band gap) are investigated as possible solutions to overcoming the challenges facing oxide integration with GaN. The cubic close-packed structure of rocksalt oxides forms a suitable epitaxial interface with the hexagonal close-packed wurtzite lattice of GaN. Three rocksalt oxide compounds are investigated in this thesis: MgO, CaO, and YbO. All are found to have a (111) MO || (0001) GaN; <1 10> MO || <11 20> GaN epitaxial relationship. Development of the epilayer microstructure is dominated by the high-energy polar growth surface (drives 3D nucleation) and the interfacial symmetry, which permits the formation of twin boundaries. Using STEM, strain relief for these ionicly bonded epilayers is observed to occur through disorder within the initial monolayer of growth. All rocksalt oxides demonstrate chemical stability with GaN to >1000°C. Concurrent MBE deposition of MgO and CaO is known to form complete solid solutions. By controlling the composition of these alloys, the oxide's lattice parameter can be engineered to match GaN and reduce interfacial state density. Compositional control is a universal challenge to oxide MBE, and the MgO-CaO system (MCO) is further complicated by magnesium's high volatility and the lack of a thermodynamically stable phase. Through a detailed investigation of MgO's deposition rate and subsequent impact on MCO composition, the process space for achieving lattice-matched compositions to GaN are fully mapped. Lattice-matched compositions are demonstrated to have the narrowest off-axis rocking curve widths ever reported for an epitaxial oxide deposited directly on GaN (0.7° in ?-circle for 200 reflection). Epitaxial deposition of the ferroelectric (Ba,Sr)TiO3 by hot RF sputtering on GaN surfaces is also demonstrated. Simple MOS capacitors are fabricated from epitaxial rocksalt oxides and (Ba,Sr)TiO3 layers deposited on n-GaN substrates. Current-voltage measurements reveal that BST epilayers have 5 orders of magnitude higher current leakage than rocksalt epilayers. This higher leakage is attributed to the smaller band offset expected at this interface; modeling confirms that electronic transport occurs by Schottky emission. In contrast, current transport across the rocksalt oxide/GaN interface occurs by Frenkel-Poole emission and can be reduced with pre-deposition surface treatments. Finally, through this work, it is realized that the integration of oxides with III-nitrides requires an appreciation of many different fields of research including materials science, surface science, and electrical engineering. By recognizing the importance that each of these fields play in designing oxide/III-nitride interfaces, this thesis has the opportunity to explore other related phenomena including accessing metastable phases through MBE (ytterbium monoxide), spinodal decomposition in metastable alloys (MCO), how polar surfaces grown by MBE compensate their bound surface charge, room temperature epitaxy, and the use of surface modification

Losego, Mark Daniel

150

Gallium arsenide and related compounds 1982; International Symposium, 10th, Albuquerque, NM, September 19-22, 1982, Contributed Papers  

NASA Astrophysics Data System (ADS)

Progress in the study of gallium arsenide and related compounds is reported. The subjects discussed include bulk and epitaxial crystal growth, optoelectronic devices, microwave devices, ion implantation, and characterization. Improvements in the preparation of high purity undoped semiinsulating GaAs are reported, and the EL2 electron trap in this material is discussed. Advances in bulk InP growth and the growth of bulk III-IV alloys are presented. The increasingly sophisticated structures being produced by research on GaAs, InP, and alloy high frequency and optoelectronic devices, including modulation-doped heterostructure charge-coupled devices, are considered. More sophisticated techniques being used for characterizing defects, deep levels, and residual impurities in GaAs, InP, and related alloys are described. No individual items are abstracted in this volume

Stillman, G. E.

151

Developmental toxicity evaluation of gallium nitrate in mice  

Microsoft Academic Search

Gallium nitrate, a drug with antitumor activity, is presently undergoing clinical trials as a chemotherapeutic agent for the treatment of certain malignancies. Since there are very limited published animal toxicity data available, this study was conducted to investigate the potential adverse developmental effects of this drug. Pregnant Swiss mice were administered intraperitoneally gallium nitrate at 12.5, 25, 50, and 100

Mercedes Gómez; Domingo J. Sánchez; José L. Domingo; Jacinto Corbella

1992-01-01

152

Automated realization of the gallium melting and triple points  

NASA Astrophysics Data System (ADS)

In order to improve the automation and convenience of the process involved in realizing the gallium fixed points, an automated apparatus, based on thermoelectric and heat pipe technologies, was designed and developed. This paper describes the apparatus design and procedures for freezing gallium mantles and realizing gallium melting and triple points. Also, investigations on the melting behavior of a gallium melting point cell and of gallium triple point cells were carried out while controlling the temperature outside the gallium point cells at 30 °C, 30.5 °C, 31 °C, and 31.5 °C. The obtained melting plateau curves show dentate temperature oscillations on the melting plateaus for the gallium point cells when thermal couplings occurred between the outer and inner liquid-solid interfaces. The maximum amplitude of the temperature fluctuations was about 1.5 mK. Therefore, the temperature oscillations can be used to indicate the ending of the equilibrium phase transitions. The duration and amplitude of such temperature oscillations depend on the temperature difference between the setting temperature and the gallium point temperature; the smaller the temperature difference, the longer the duration of both the melting plateaus and the temperature fluctuations.

Yan, X.; Duan, Y.; Zhang, J. T.; Wang, W.

2013-09-01

153

First results from the Soviet-American gallium experiment  

Microsoft Academic Search

The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95%

A. I. Abazov; D. N. Abdurashitov; O. L. Anosov; L. A. Eroshkina; E. L. Faizov; V. N. Gavrin; A. V. Kalikhov; T. V. Knodel; I. I. Knyshenko; V. N. Kornoukhov; S. A. Mezentseva; I. N. Mirmov; A. I. Ostrinsky; V. V. Petukhov; A. M. Pshukov; N. Ye. Revzin; A. A. Shikhin; P. V. Timofeyev; E. P. Veretenkin; V. M. Vermul; Yu. Zakharov; G. T. Zatsepin; V. I. Zhandarov; T. J. Bowles; B. T. Cleveland; S. R. Elliott; H. A. O'Brien; D. L. Wark; J. F. Wilkerson; R. Davis; K. Lande; M. L. Cherry; R. T. Kouzes

1991-01-01

154

Dispersion of submicron Ni particles into liquid gallium  

Microsoft Academic Search

In this paper a liquid gallium with a low melting temperature and good thermal conductivity was used as a carrier to develop a new magnetorheological (MR) fluid that can be employed in energy convection devices. Submicron nickel particles, coated with silica, were chosen to be dispersed in the liquid gallium. The silica coating was used to improve the dispersion and

L. F. Cao; H. S. Park; G. Dodbiba; T. Fujita

2008-01-01

155

ASSESSMENT OF ARSENIC EXPOSURES AND CONTROLS IN GALLIUM ARSENIDE PRODUCTION  

Microsoft Academic Search

The electronics industry is expanding the use of gallium arsenide in the production of optoelectronic devices and integrated circuits. Workers in the electronics industry using gallium arsenide are exposed to hazardous substances such as arsenic, arsine, and various acids. Arsenic requires stringent controls to minimize exposures (the current OSHA PEL for arsenic is 10 ?\\/m3 and the NIOSH REL is

John W. Sheehy; James H. Jones

1993-01-01

156

Crystal Growth of Gallium Arsenide using Carbon Boats  

Microsoft Academic Search

GALLIUM arsenide is a semiconductor of great interest from the purely scientific point of view and as a device material. It is therefore desirable to be able to prepare single crystals of high purity. Because of the reactive nature of gallium liquid and arsenic vapour at high temperature, only a limited number of refractories may be used as boat materials

J. R. Knight

1961-01-01

157

Gallium nitride hybrid microwave circuits for low-noise applications  

Microsoft Academic Search

This paper presents recent work in the area of gallium nitride (GaN) low-noise microwave integrated circuits. Gallium nitride has attracted interest principally due to its power handling ability. However, its noise performance has received relatively little attention. We discuss the noise performance of several discrete devices, and how they perform in hybrid integrated circuits. The predictive and descriptive models used

Tyler Ross; Gabriel Cormier; Khelifa Hettak

2010-01-01

158

Role of gallium-67 in the clinical evaluation of cancer  

Microsoft Academic Search

This review is based primarily on historic data, and it examines the indications for and limitations of gallium-67 scanning in the evaluation of patients with neoplasms. The use of gallium-67 scans is discussed according to tumor type, and data from the most representative and comprehensive studies are included. The results described, some of which were obtained primarily with older imaging

C. Bekerman; P. B. Hoffer; J. D. Bitran

1984-01-01

159

Enrichment behaviour of gallium in heat and surface treatments of Al–Ga foils  

Microsoft Academic Search

The behaviour of gallium is examined after heat and surface treatments of aluminium foils containing either 120 or 1300 ppm gallium, with low enrichments of gallium at the surfaces arising from foil manufacture. Vacuum heat treatment at 823 K for 20 ks caused negligible additional enrichment, probably associated with the high solubility of gallium in aluminium. Subsequent alkaline etching in

Z. Ashitaka; P. Skeldon; G. E. Thompson; K. Shimizu; H. Habazaki

2002-01-01

160

Nuclear microprobe imaging of gallium nitrate in cancer cells  

NASA Astrophysics Data System (ADS)

Gallium nitrate is used in clinical oncology as treatment for hypercalcemia and for cancer that has spread to the bone. Its mechanism of antitumor action has not been fully elucidated yet. The knowledge of the intracellular distribution of anticancer drugs is of particular interest in oncology to better understand their cellular pharmacology. In addition, most metal-based anticancer compounds interact with endogenous trace elements in cells, altering their metabolism. The purpose of this experiment was to examine, by use of nuclear microprobe analysis, the cellular distribution of gallium and endogenous trace elements within cancer cells exposed to gallium nitrate. In a majority of cellular analyses, gallium was found homogeneously distributed in cells following the distribution of carbon. In a smaller number of cells, however, gallium appeared concentrated together with P, Ca and Fe within round structures of about 2-5 ?m diameter located in the perinuclear region. These intracellular structures are typical of lysosomial material.

Ortega, Richard; Suda, Asami; Devès, Guillaume

2003-09-01

161

The Characterization and Dissolution of Scrub Alloy Buttons in F-Canyon  

SciTech Connect

The second series of scrub alloy material characterization and dissolution studies has been performed on samples collected from scrub alloy buttons now stored at the Savannah River Site. The need for the additional laboratory work became necessary after it was established that two of the original scrub alloy buttons selected for analysis were not representative of the materials present in their respective categories. One of the categories re-examined contained plutonium-aluminum alloys and the other category contained plutonium-gallium alloys.

Gray, J.H.

2001-02-20

162

Targeting Iron-Dependent DNA Synthesis with Gallium and Transferrin-Gallium  

Microsoft Academic Search

While iron is essential for numerous intracellular processes, its critical role in DNA synthesis relates to the activity of the iron-containing M2 subunit of ribonucleotide reductase, the enzyme responsible for the synthesis of deoxyribonucleotides. Gallium, a metal which resembles iron with respect to transferrin (Tf) binding, cellular uptake by the Tf receptor and incorporation into ferritin, blocks the cellular uptake

Christopher R. Chitambar; Jana Narasimhan

1991-01-01

163

Gallium scintigraphic pattern in lung CMV infections  

SciTech Connect

Due to extensive use of prophylactic therapy for Pneumonitis Carinii Pneumonia (PCP), Cytomegalic Viral (CMV) infection may now be the most common lung infection in AIDS patients. This study was performed to determine Gallium-67 patterns in AIDS patients with CMV. Pathology reports were reviewed in AIDS patients who had a dose of 5 to 10 mCi of Gallium-67 citrate. Analysis of images were obtained 48-72 hours later of the entire body was performed. Gallium-67 scans in 14 AIDS patients with biopsy proven CMV, were evaluated for eye, colon, adrenal, lung and renal uptake. These were compared to 40 AIDS patients without CMV. These controls had infections including PCP, Mycobacterial infections, and lymphocytic interstitial pneumonitis. 100% of CMV patients had bowel uptake greater than or equal to liver. Similar bowel activity was seen in 50% of AIDS patients without CMV. 71% had intense eye uptake which was seen in only 10% of patients without CMV. 50% of CMV patients had renal uptake compared to 5% of non-CMV cases. Adrenal uptake was suggested in 50%, however, SPECT imaging is needed for confirmation. 85% had low grade lung uptake. The low grade lung had perihilar prominence. The remaining 15% had high grade lung uptake (greater than sternum) due to superimposed PCP infection. Colon uptake is very sensitive indicator for CMV infection. However, observing eye, renal, and or adrenal uptake improved the diagnostic specificity. SPECT imaging is needed to confirm renal or adrenal abnormalities due to intense bowel activity present in 100% of cases. When high grade lung uptake is seen superimposed PCP is suggested.

Ganz, W.I.; Cohen, D.; Mallin, W. [Univ. of Miami School of Medicine, FL (United States)] [and others

1994-05-01

164

Gallium-67 imaging in muscular sarcoidosis  

SciTech Connect

A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid muscle disease but is consistent with the rarity of clinical evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

1984-07-01

165

Behavior of Zircaloy Cladding in the Presence of Gallium  

SciTech Connect

The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid metal embrittlement was observed.

DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.; Wilson, D.F.

1998-09-28

166

Mechanism of gallium-67 accumulation in tumors  

SciTech Connect

Neoplasms are characterized by increased perfusion, increased permeability of their capillary beds to macromolecules, and a delay in new lymphatic vessel growth. These lead to the increased entry and residency time of macromolecules in the interstitial space of tumors. Multiple factors contribute to the localization of /sup 67/Ga in tumors. Adequate blood supply is essential; at areas with no blood supply such as the necrotic center of a large tumor, there is no /sup 67/Ga accumulation. Gallium-67, mainly in the form of transferrin-67Ga complex, is delivered to the tumor through capillaries with increased permeability. In tumors, some /sup 67/Ga is taken up by tumor cells; some may also be taken up by inflammatory cells when they are present. Gallium-67 binding proteins, such as lactoferrin or ferritin, may also contribute to the accumulation and retention of /sup 67/Ga in tumors; however, their roles are less clear. The intensity of these various factors determine their relative contribution and the degree of /sup 67/Ga accumulation in tumors.56 references.

Tsan, M.F.; Scheffel, U.

1986-07-01

167

Gallium scanning in lymphoid interstitial pneumonitis of children with AIDS  

SciTech Connect

Lymphoid interstitial pneumonitis (LIP) is a frequent pulmonary complication in the child with the acquired immune deficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection. We report the gallium scan findings in two children with AIDS and LIP. Gallium scintigraphy in both children demonstrated increased radionuclide concentration throughout the lungs, a pattern indistinguishable scintigraphically from that of Pneumocystis carinii pneumonia (PCP). This should alert nuclear medicine practitioners and referring physicians to another cause of diffusely increased gallium uptake in the lungs of patients with AIDS.

Schiff, R.G.; Kabat, L.; Kamani, N.

1987-12-01

168

Infrared Response of Impurity Doped Silicon MOSFET's (IRFET's): Fabrication and Characterization of the Gallium Doped Infrared Sensing MOSFET.  

National Technical Information Service (NTIS)

Fabrication and characterization of the gallium doped infrared sensing MOSFET is described. Gallium doped MOSFET device structures have been fabricated by diffusion of gallium from doped oxide sources into n-channel MOSFET's fabricated on a normal boron p...

L. Forbes

1976-01-01

169

Fabrication, performance and degradation mechanism of aluminum gallium nitride/gallium nitride heterostructure field-effect transistors  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) has attracted a lot of attention as the next generation of semiconductor material for microwave power application. The unique and superior material properties of GaN and its heterostructure, such as excellent transport property, high breakdown voltage and sheet carrier concentration, and thermal and mechanical stabilities, enable AlGaN/GaN heterostructure field effect transistors (HFETs) to deliver unprecedented levels of microwave power performance. Potential applications include ultra-wide bandwidth communications and radar systems, wireless base stations, and communications satellites. Tremendous efforts to realize the potential of Al-GaN/GaN HFETs have been made over the last decade focusing on improving microwave power performance via optimizing material growth and semiconductor processing technologies. As the device performance is getting mature, the device's reliability becomes a major concern for manufacturability of commercially available AlGaN/GaN HFETs. However, comprehensive study on the reliability of these devices is still lacking. This dissertation describes the fabrication, performance and degradation characteristics and mechanism of AlGaN/GaN HFETs. The devices were fabricated with alloyed Ti/Al/Ti/Au ohmic contact and Ni/Au mushroom gate contact using E-beam lithography. The device's microwave performance was significantly improved after SiN passivation due to reduced surface effects. Several degradation modes, primarily a decrease of the output current and microwave output power density, were observed under various electrical stress tests including high current stress, high field stress, and RF overdrive. To further investigate the physical mechanism of observed degradations, SiN passivation, pulsed IV (gate lag), low frequency noise measurements, deep level transient spectroscopy (DLTS), and scanning kelvin probe microscopy (SKPM) have all been employed with hot electron stress testing. The results clearly demonstrated that charge accumulation and trap creation at the semiconductor surface and interface induced by hot electron effects are responsible for observed degradation.

Kim, Hyungtak

170

Preparation and characterization of p-type transparent conducting tin-gallium oxide films  

NASA Astrophysics Data System (ADS)

p-Type transparent conducting tin-gallium oxide (TGO) films were successfully fabricated on quartz substrates by DC magnetron sputtering of GaSn alloy films followed by thermal oxidation. XRD characterization indicated that the TGO films maintain rutile structure of the tin oxide (SnO2). UV vis transmittance spectra indicated that the films have a transmittance higher than 85% in the visible region, with an optical band-gap around 3.8 eV. Hall effect measurement showed that electrical properties of the TGO films were dependent on oxidation temperature. Oxidation at too high or low temperature was unfavorable for p-type conduction. It is found that the optimum oxidation temperature for highest hole concentration (8.84 × 1018 cm-3) was in the range of 600 650 °C.

Huang, Yixian; Ji, Zhenguo; Chen, Chen

2007-03-01

171

Epitaxial Growth of Bulk-Quality Gallium Arsenide on Gallium Arsenide and Germanium Substrates  

Microsoft Academic Search

l-4 Efferl has reported high electron mobilities in homoepitaxial gallium arsenide but otherwise little is known about the electrical properties or the crystal perfection of these layers. In our work, epitaxial growth was effected using a hydrogen stream saturated at room temperature with AsCla (p= 10 mm) passing first over metallic Ga at 900°C and then over GaAs or Ge

L. C. Bobb; H. Holloway; K. H. Maxwell; E. Zimmerman

1966-01-01

172

Density functional study of the effects of doping and stoichiometry on gallium diffusion in gallium arsenide  

NASA Astrophysics Data System (ADS)

Previous experimental [1-4] and theoretical [5,6] work on the properties of diffusion of gallium within gallium arsenide has produced some results that are apparently at odds with each other. We present results of a wide theoretical survey of the point defects that form in this material with special attention paid to the formation and diffusion of excess-gallium-related point defects. In this study we applied density functional theory in the local density approximation [7]. Diffusion was examined through the use of the nudged elastic band method [8]. After considering the accuracy of the approximations used, the calculations yield information compatible with the experimental situation and capable of shedding light on areas of apparent disagreement.[4pt] [1] G B"osker et al., Phys. Rev. B 52, 11927 (1995). [2] G B"osker et al., J. Appl. Phys. 86, 791 (1999). [3] H Bracht and S Brotzmann, Phys. Rev. B 71, 115216 (2005). [4] H Bracht et al., Physica B 308-210, 831 (2001). [5] K Levasseur-Smith and N. Mousseau, J. Appl. Phys. 103, 113502 (2008). [6] PA Schultz et al., Mod. and Sim. in Mat. Sci. and Engr. 17, 084007 (2009). [7] G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993); ibid. 49, 14251 (1994). [8] H. J'onsson et al., "Classical and quantum dynamics in condensed phase systems," (World Scientific, 1998) Chap. 16, pp. 385-404.

Schick, J. T.; Morgan, C. G.

2011-03-01

173

Radiation Tolerant, High Speed, Low Power, Gallium Arsenide Logic.  

National Technical Information Service (NTIS)

Gallium Arsenide (GaAs) circuits are largely immune to slowly accumulated radiation doses and therefore do not need the shielding required by complementary metal oxide semiconductor (CMOS) devices. This attribute renders GaAs circuits particularly attract...

K. A. Wolfe

1993-01-01

174

All-optical modulation in gallium arsenide integrated optical waveguides  

SciTech Connect

We have investigated all-optical modulators in gallium arsenide integrated optical waveguides; these modulators use electron-hole pair generation to alter the propagation characteristics of a guided light beam. 6 refs., 6 figs.

McWright, G.; Ross, B.; Guthreau, W.; Lafaw, D.; Lowry, M.; Tindall, W.

1988-01-27

175

Quantum-Optical Integrated Circuits of Gallium Arsenide.  

National Technical Information Service (NTIS)

The report describes quantum-optical logic circuits of gallium arsenide, developed using methods of semiconductor integrated technology. Laser integrated modules were made with electron-hole junctions formed by the diffusion method. The modules are made a...

I. S. Goldobin A. S. Dobkin

1971-01-01

176

Gallium phosphide nanowires as a substrate for cultured neurons.  

PubMed

Dissociated sensory neurons were cultured on epitaxial gallium phosphide (GaP) nanowires grown vertically from a gallium phosphide surface. Substrates covered by 2.5 microm long, 50 nm wide nanowires supported cell adhesion and axonal outgrowth. Cell survival was better on nanowire substrates than on planar control substrates. The cells interacted closely with the nanostructures, and cells penetrated by hundreds of wires were observed as well as wire bending due to forces exerted by the cells. PMID:17880143

Hällström, Waldemar; Mårtensson, Thomas; Prinz, Christelle; Gustavsson, Per; Montelius, Lars; Samuelson, Lars; Kanje, Martin

2007-09-19

177

Light Induced Soliton Switching at the Gallium-Silica Interface  

NASA Astrophysics Data System (ADS)

In the present paper, we have investigated the solitonic characteristics of a pulse passing through an interface separating two nonlinear media. The first media is a thin film of gallium nanoparticles which show switching properties under optical excitation and second is a monomode optical fiber. Soliton propagation in three different phases of gallium nanoparticles have been analyzed by using the method of phase-plane analysis. Also, the critical power required for soliton propagation has been calculated.

Naruka, Preeti; Bissa, Shivangi

178

Positive gallium-67 scintigraphy associated with pulmonary embolism  

SciTech Connect

A 54-year-old man presenting with symptoms and signs of pulmonary embolism demonstrated gallium-67 accumulation within the right lower lung field in the region of a pulmonary embolism with effusion. An associated infectious process was ruled out. This is contrary to the usual clinical experience and identifies a potential pitfall in the use of gallium-67 as an aid in the differential diagnosis of pulmonary embolism and pneumonitis.

Brown, J.M.; Moreno, A.J.; Weisman, I.; Baker, F.J.; Lundy, M.N.; Brown, T.J.

1983-08-01

179

Selective catalytic reduction of NO with methane on gallium catalysts  

Microsoft Academic Search

Gallium species supported on H-ZSM-5 and on H-mordenite are active catalysts for NO reduction with methane in the presence of excess O[sub 2]. Over Ga-H-ZSM-5, the NO reduction rate is first order in NO with a variable, fractional order in CH[sub 4]. The distinct feature of these gallium-based catalysts is their very high CH[sub 4] selectivities for NO[sub x] reduction.

Yuejin Li; J. N. Armor

1994-01-01

180

Role of gallium-67 in the clinical evaluation of cancer  

SciTech Connect

This review is based primarily on historic data, and it examines the indications for and limitations of gallium-67 scanning in the evaluation of patients with neoplasms. The use of gallium-67 scans is discussed according to tumor type, and data from the most representative and comprehensive studies are included. The results described, some of which were obtained primarily with older imaging techniques, should be regarded as representing the minimum that can be expected from application of this imaging procedure.

Bekerman, C.; Hoffer, P.B.; Bitran, J.D.

1984-10-01

181

Gallium arsenide clusters and their interfacial physics and chemistry  

Microsoft Academic Search

Gallium arsenide clusters have been studied on a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer with an external supersonic cluster source. Reaction of GaAs cluster cations with ammonia revealed that all cluster cations larger than seven atoms were most reactive near the 1\\/1 composition ratio of gallium\\/arsenic. The results suggest that even at this small size, the clusters begin

Richard E. Smalley; Robert F. Curl; Frank K. Tittel

1992-01-01

182

Inhalation developmental toxicology studies: Gallium arsenide in mice and rats  

SciTech Connect

Gallium arsenide is a crystalline compound used extensively in the semiconductor industry. Workers preparing solar cells and gallium arsenide ingots and wafers are potentially at risk from the inhalation of gallium arsenide dust. The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague- Dawley rats and CD-1 (Swiss) mice exposed to 0, 10, 37, or 75 mg/m{sup 3} gallium arsenide, 6 h/day, 7 days/week. Each of the four treatment groups consisted of 10 virgin females (for comparison), and {approx}30 positively mated rats or {approx}24 positively mated mice. Mice were exposed on 4--17 days of gestation (dg), and rats on 4--19 dg. The day of plug or sperm detection was designated as 0 dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. Gallium and arsenic concentrations were determined in the maternal blood and uterine contents of the rats (3/group) at 7, 14, and 20 dg. 37 refs., 11 figs., 30 tabs.

Mast, T.J.; Greenspan, B.J.; Dill, J.A.; Stoney, K.H.; Evanoff, J.J.; Rommereim, R.L.

1990-12-01

183

An effective interaction potential for gallium phosphide.  

PubMed

An effective interatomic potential consisting of two- and three-body covalent interactions is used here to study the properties of gallium phosphide by molecular dynamics simulations. The many-body interatomic potential accounts for the energy scale, length scale and mechanical properties of GaP. At atmospheric pressure, the calculated melting temperature, linear thermal expansion, vibrational density of states and specific heat are in excellent agreement with experimental results. The structural phase transition induced by hydrostatic pressure at 27 GPa is also in quite good agreement with experimental findings. We also studied the energy of vacancy formation in the GaP lattice and the surface energy, which is in reasonable agreement with experimental data. PMID:21406914

Ribeiro-Silva, C I; Rino, J P; Gonçalves, Luis G V; Picinin, A

2011-01-13

184

Direct band gap wurtzite gallium phosphide nanowires.  

PubMed

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555-690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

Assali, S; Zardo, I; Plissard, S; Kriegner, D; Verheijen, M A; Bauer, G; Meijerink, A; Belabbes, A; Bechstedt, F; Haverkort, J E M; Bakkers, E P A M

2013-03-18

185

Direct Band Gap Wurtzite Gallium Phosphide Nanowires  

PubMed Central

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality.

2013-01-01

186

Gallium-68 lipophilic complexes for labeling platelets  

SciTech Connect

Generator produced 68Ga-labeled platelets could be useful for positron emission tomographic (PET) studies of thrombosis or atherosclerosis. To label platelets with 68Ga, we have studied the effects of trace metals in elutions of 68Ga from 68Ge. Studies were conducted on the formation of lipophilic 68Ga complexes 8-hydroxyquinoline, tropolone, and mercaptopyridine-N-oxide (MPO). Parameters such as pH, buffers, concentration of ligand, and stability with time were investigated. High performance liquid chromatography and instant thin layer chromatography were used to quantitate formation of the 68Ga complex. Platelets from human, dog, and rabbit plasma were incubated with the 68Ga complexes and the percent labeling determined. Accumulation of platelets in the catheter scraped aorta of the rabbit was determined by PET imaging, tissue counting, and autoradiography. Gallium-68 MPO gave 40-60% labeling of rabbit platelets with higher accumulation in the scraped aorta compared to the normal.

Yano, Y.; Budinger, T.F.; Ebbe, S.N.; Mathis, C.A.; Singh, M.; Brennan, K.M.; Moyer, B.R.

1985-12-01

187

Gallium arsenide: Solar panel assembly technology  

SciTech Connect

Gallium arsenide (GaAs) solar cell devices are maturing at 18% AMO efficiencies for liquid phase epitaxy (LPE) technology, and efforts must be intensified placing necessary focus on the development of panel assembly techniques, and ultimately panel manufacturing methods capable of maintaining these high efficiencies for on-panel operation. Key problems and solutions are described which were experienced during the assembly of flight qualified solar panels using Spectrolab's mature (silicon) panel manufacturing processes for assembly of LPE GaAs solar cells. These cells were produced by Hughes Malibu (supplied by the U.S. Air Force WPAFB) ranging in efficiency from 15 to 17 percent, air mass zero (AMO) 28 degrees C. Cell assembly methods for coverglass installation, submodule, and circuit soldering, as well as panel bonding are discussed. The LIPS II satellite, using a GaAs solar cell panel was successfully launched in 1983.

Zemmrich, D.; Loo, R.; Mardesich, N.; McFarlane, B.

1984-05-01

188

The Soviet-American Gallium Experiment (SAGE)  

SciTech Connect

It is a great pleasure for me to have been asked by Louis Rosen to tell you about the Soviet-American Gallium Experiment (SAGE). This undertaking is a multi-institutional collaboration among scientists from the Institute for Nuclear Research, Moscow (INR), Los Alamos National Laboratory (LANL), and several US universities. Its purpose is to measure the number of low-energy electron neutrinos emitted from the Sun that arrive at this planet. As such, it is an extremely important experiment, touching on fundamental physics issues as well as solar dynamics. In contrast to the strategic overviews, plans, and hopes for international collaboration presented earlier today, SAGE is an ongoing working effort with high hopes of producing the first measurement of the Sun's low-energy neutrino flux. This paper reviews this experiment. 3 refs., 3 figs.

Garvey, G.T.

1989-01-01

189

Cathodoluminescence spectra of gallium nitride nanorods  

PubMed Central

Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

2011-01-01

190

Optical properties of gadolinium gallium garnet.  

PubMed

The refractive index, the temperature coefficient of the refractive index, and the optical transparency of gadolinium gallium garnet are reported as a function of wavelength from the near UV to the middle IR. The materialis transparent enough for good optical components between 0.36 and 6.0 microm, and the refractive index ranges from 2.0 at the UV end to 1.8 at the IR end of the spectrum. The wavelength dependence of index is expressed as a three-term Sellmeier formula with agreement better than two parts in the fourth decimal between calculated and experimental values. Variations in composition depending on growth from various melts (e.g., stoichiometric vs congruent) have no effect on the optical parameters at this level of precision. PMID:20567472

Wood, D L; Nassau, K

1990-09-01

191

Modified permittivity observed in bulk Gallium Arsenide and Gallium Phosphide samples at 50 K using the Whispering Gallery mode method  

Microsoft Academic Search

Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium\\u000aPhosphide samples have been examined both in darkness and under white light at\\u000a50 K. In both samples we observed change in permittivity under light and dark\\u000aconditions. This results from a change in the polarization state of the\\u000asemiconductor, which is consistent with a free electron-hole\\u000acreation\\/recombination process. The

John G. Hartnett; David Mouneyrac; Jean-Michel Le Floch; Jerzy Krupka; Michael E. Tobar; D. Cros

2009-01-01

192

Use of Whispering-Gallery Modes and Quasi Modes for Broadband Characterization of Bulk Gallium Arsenide and Gallium Phosphide Samples  

Microsoft Academic Search

The complex permittivity of bulk crystals of semiinsulating gallium arsenide (GaAs) and gallium phosphide (GaP) were measured over the frequency range from 4 to 30 GHz and at temperatures from 30 up to 300 K employing whispering-gallery-mode (WGM) and quasi-TE0 np-mode dielectric-resonator techniques. At temperatures about 40 K, dielectric loss tangent values were below 10 -6 for GaAs and below

Jerzy Krupka; David Mouneyrac; John G. Hartnett; Michael E. Tobar

2008-01-01

193

Thermodynamique des alliages (U,Fe) et (U,Ga) en spectrometrie de masse a haute temperature. (Thermodynamics of (U,Fe) and (U,Ga) alloys in high temperature mass spectrometry).  

National Technical Information Service (NTIS)

From iron and gallium activity measurements in liquid U-Fe and U-Ga alloys, partial molar free enthalpies for excess of each element of the alloys are given in function of temperature and concentration: these energies are correctly represented by Margules...

P. Gardie J. J. Poupeau G. Bordier J. Le Ny

1991-01-01

194

Application of ultrasound in solvent extraction of nickel and gallium  

SciTech Connect

The effects of ultrasound on the rate of solvent extraction of nickel with Lix 65N and Lix 70, and gallium with Kelex 100 were investigated. These solvent extraction systems are noted by their sluggish nature. Low frequency (20 kHz) ultrasound increased the rates of extraction of nickel by factors of four to seven. The ultrasound had no effect on the final chemical equilibrium. Gallium extraction rates were enhanced with the use of ultrasound by as much as a factor of 15. Again, the ultrasound had no effect on extraction equilibrium. For both nickel and gallium, the enhanced rates were attributed to increased interfacial surface area associated with ultrasonically induced cavitation and microdroplet formation. The stability of the microdroplets permitted intermittent application of ultrasound with corresponding decreases in ultrasonic energy requirements. The lowest energy consumption was observed with short (0.25 to 5 s) bursts of high power (41 to 61 W) ultrasonic inputs. The study also provided insight into the factors that affect the complex extraction of gallium from sodium aluminate solutions. The rate controlling step was found to be the dehydration of the gallate ion, Ga(OH)4, and the first complex formation between gallium and Kelex 100. Sodium was found to enhance the extraction rate up to a point, beyond which increased concentration was detrimental. Increasing aluminum concentration was found to slow extraction rates. Modifiers and diluents were shown to markedly affect extraction rates even without ultrasound. Ketone modifiers, particularly 2-undecanone, when used with Kermac 470B or Escaid 200 diluents enhanced extraction rates of gallium to the point that the use of ultrasound provided no additional benefits. The positive effects of ketone modifiers for the solvent extraction of gallium had not been previously reported.

Pesic, B.

1996-07-01

195

Growth and characterization of molecular beam epitaxial gallium arsenide antimonide and gallium arsenide antimonide/gallium arsenide superlattices  

SciTech Connect

Described in this thesis are the molecular-beam epitaxial growth and characterization of GaAs/sub 1-x/Sb/sub x/ films and GaAs/sub 1-x/Sb/sub x//GaAs strained-layer superlattices. The methods used to reproducibly grow GaAs/sub 1-x/Sb/sub x/ across its entire composition range are detailed. The resulting film surface morphologies and microstructures are investigated by optical and electron microscopy. Significant atomic clustering and ordering effects are observed in alloys of metastable composition. Optical characterization of these alloys shows good-quality material can be obtained, but the major limitation to the quality of these materials is related to the film microstructure. Electrical measurements on unintentionally-doped layers reveal p-type conductivity due to two distinct acceptor levels. Hole mobilities are qualitatively explained in a model that assumes a dominant alloy scattering mechanism.

Klem, J.F.

1987-01-01

196

Gallium a unique anti-resorptive agent in bone: Preclinical studies on its mechanisms of action  

SciTech Connect

The discovery of gallium as a new and unique agent for the treatment of metabolic bone disorders was in part fortuitous. Gallium is an exciting new therapeutic agent for the treatment of pathologic states characterized by accelerated bone resorption. Compared to other therapeutic metal compounds containing platinum or germanium, gallium affects its antiresorptive action without any evidence of a cytotoxic effect on bone cells. Gallium is unique amongst all therapeutically available antiresorptive agents in that it favors bone formation. 18 refs., 1 fig.

Bockman, R.; Adelman, R.; Donnelly, R.; Brody, L.; Warrell, R. (Hospital for Special Surgery, New York, NY (USA)); Jones, K.W. (Brookhaven National Lab., Upton, NY (USA))

1990-01-01

197

Gallium-67/stable gadolinium antagonism: MRI contrast agent markedly alters the normal biodistribution of gallium-67  

SciTech Connect

An 11-yr-old patient was scanned 96 hr after the administration of gallium-67 ({sup 67}Ga). The scan emulated the biodistribution of a typical bone-seeking radipharmaceutical-rather than that of {sup 67}Ga. None of the factors previously identified with alteration of the biodistribution of {sup 67}Ga were found. However, the patient had been injected with gadopentetate in conjunction with magnetic resonance imaging 4 hr before receiving the {sup 67}Ga. Gadolinium appears to cause a strong carrier-like effect in {sup 67}Ga scans.

Hattner, R.S.; White, D.L. (Univ. of California, San Francisco (USA))

1990-11-01

198

Ultraviolet light-driven epitaxial growth of gallium arsenide at reduced substrate temperatures  

Microsoft Academic Search

We report on the photodeposition of gallium arsenide on gallium arsenide and silicon at low substrate temperatures utilizing ultraviolet radiation. A 1000 W Hg-Xe arc lamp serves as the light source with triethylgallium and arsine serving as the reactants. In this study, single crystal gallium arsenide thin films are obtained at substrate temperatures of approximately 357°. The electrical, chemical and

D. P. Norton; P. K. Ajmera

1990-01-01

199

Foundations of ohmic contact formation on aluminum gallium nitride/gallium nitride heterostructures  

NASA Astrophysics Data System (ADS)

Aluminum gallium nitride (AlGaN)/gallium nitride (GaN) high electron mobility transistors (HEMTs) have tremendous potential for application in high frequencies, high temperatures and microwave and mm power amplifications. Fabrication of Ohmic contacts for such devices that meet the stringent low-resistance, high thermal stability and smooth surface morphology requirements has been challenging. In the cases where Ohmic behavior can be achieved, a full scientific understanding of the mechanism(s) through which Ohmic behavior is achieved, as well as the effects of metal interlayer thicknesses, surface preparation, annealing ambient, and interfacial reaction products, is yet to emerge. A such, the focus of this work centers on the investigation of design, processing and materials' issues in the development and optimization of stable Ohmic contacts to AlGaN/GaN heterostructure epilayers in order to begin to address some of these issues. Multilayer Ohmic contact schemes are designed, fabricated and characterized. Design of contact schemes is tailored to enable the identification of the roles constituent components play in achieving Ohmic behavior. The understanding gained from such students has allowed for controlling and optimization of interfacial and intermetallic reactions, and enabled the fabrication of low-resistance contacts with large processing window and high-temperature thermal stability. The outcome of this work lays the foundation for not only the design and fabrication of Ohmic contacts with excellent properties, but also the understanding of Ohmic contact formation mechanisms on AlGaN/GaN heterostructures.

Mohammed, Fitih Mustefa

200

Synthesis and characterization of gallium colloidal nanoparticles.  

PubMed

In this work, gallium colloidal nanoparticles (Ga-Nps) were synthesized by chemical liquid deposition (CLD). This method involved the deposition of metallic atoms with organic solvents (THF, acetone and 2-propanol) in a freezing matrix of the solvent at 77K, in order to obtain core-shell Ga-Nps which were characterized by: FT-IR, UV-Vis, TEM, SAED and electrophoretic mobility measurements. TEM images revealed a wide distribution of the apparent size of the particles and apparent average size of 5.65, 8.11 and 13.87 nm for Ga-Nps obtained with 2-propanol, THF and acetone, respectively. UV spectra showed absorption bands of metal plasmons, interesting quantum size effects and plasmon absorption bands of particles aggregated to lambda(280) and lambda(325). Electrophoretic mobility allowed to evidence that nanoparticles had a negative charge as well as to observe that the zeta potential of the colloidal dispersions decreased over time, showing a significant tendency to the aggregation of Ga-Nps. The importance of the functionalization of metal nanoparticles with high dielectric constant solvents in the stabilization of colloidal systems was also observed. FT-IR spectroscopy revealed that the interaction of Ga surface with the solvent possibly produces a (GaC) bond. Experimental details, structural and thermal stability studies were also analyzed in this work. PMID:20378122

Meléndrez, M F; Cárdenas, G; Arbiol, J

2010-01-20

201

Proportional counter response calculations for gallium solar neutrino detectors  

NASA Astrophysics Data System (ADS)

Gallium-based solar neutrino detectors are sensitive to the primary pp reaction in the sun. Two experiments using gallium, SAGE in the Soviet Union and GALLEX in Europe, are under construction and are scheduled to produce data by 1989. The radioactive 71Ge produced by neutrinos interacting with the gallium detector material is chemically extracted and counted in miniature proportional counters. A number of calculations have been carried out to simulate the response of these counters to the decay of 71Ge and to background events. It is shown that the use of xenon gas clearly improves the detector efficiency relative to argon in the 10-keV energy range from 35 percent to 53 percent. It appears that the disadvantage of increased conversion efficiency for background gammas in xenon is not relevant, due to the dominance of the conversion of gammas in the glass walls of the detector.

Kouzes, R. T.; Reynolds, D.

1989-02-01

202

The Soviet-American gallium experiment at Baksan  

SciTech Connect

A gallium solar neutrino detector is sensitive to the full range of the solar neutrino spectrum, including the low-energy neutrinos from the fundamental proton-proton fusion reaction. If neutrino oscillations in the solar interior are responsible for the suppressed {sup 8}B flux measured by the Homestake {sup 37}Cl experiment and the Kamiokande water Cherenkov detector, then a comparison of the gallium, chlorine, and water results may make possible a determination of the neutrino mass difference and mixing angle. A 30-ton gallium detector is currently operating in the Baksan laboratory in the Soviet Union, with a ratio of expected solar signal to measured background (during the first one to two {sup 71}Ge half lives) of approximately one. 28 refs.

Abazov, A. I.; Abdurashitov, D. N.; Anosov, O. L.; Danshin, S. N.; Eroshkina, L. A.; Faizov, E. L.; Gavrin, V. N.; Kalikhov, A. V.; Knodel, T. V.; Knyshenko, I. I.; Kornoukhov, V. N.; Mezentseva, S. A.; Mirmov, I. N.; Ostrinsky, A. I.; Petukhov, V. V; Pshukov, A. M.; Revzin, N. Ye; Shikhin, A. A.; Slyusareva, Ye. D.; Timofeyev, P. V.; Veretenkin, E. P.; Vermul, V. M.; Yantz, V. E.; Zakharov, Yu.; Zatsepin, G. T.; Zhandarov, V. I. [AN SSSR, Mosco

1990-01-01

203

Reaction of gallium arsenide with concentrated acids: formation of arsine.  

PubMed

Crystalline particles of gallium arsenide (GaAs) (approximately 2 microns in diameter) react with concentrated hydrochloric acid (HCl) (11.6 to 9 M) to form highly toxic arsine (AsH3) gas. None of the other strong acids that were investigated reacted with gallium arsenide to form AsH3. A spectrophotometric method, based on the reaction of AsH3 with silver diethyldithiocarbamate in a chloroform solution containing morpholine, was used to detect AsH3 gas dissolved in aqueous solutions and to determine the AsH3 gas that was liberated by the reaction of GaAs with HCl. Active sites on the gallium arsenide surface initiate the reaction that forms AsH3 gas. Absorption of oxygen or ions from solution on these active sites inhibits the formation of AsH3. PMID:2756869

Scott, N; Carter, D E; Fernando, Q

1989-07-01

204

Interaction of a Liquid Gallium Jet with ISTTOK Edge Plasmas  

NASA Astrophysics Data System (ADS)

The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages in the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaust from fusion devices. Presently the most promising candidate materials are lithium and gallium. However, lithium has a short liquid state range when compared, for example, with gallium that has essentially better thermal properties and lower vapor pressure. To explore further these properties, ISTTOK tokamak is being used to test the interaction of a free flying, fully formed liquid gallium jet with the plasma. The interacting, 2.3 mm diameter, jet is generated by hydrostatic pressure and has a 2.5 m/s flow velocity. The liquid metal injector has been build to allow the positioning of the jet inside the tokamak chamber, within a 13 mm range. This paper presents the first obtained experimental results concerning the liquid gallium jet-plasma interaction. A stable jet has been obtained, which was not noticeably affected by the magnetic field transients. ISTTOK has been successfully operated with the gallium jet without degradation of the discharge or a significant plasma contamination by liquid metal. This observation is supported by spectroscopic measurements showing that gallium radiation is limited to the region around the jet. Furthermore, the power deposited on the jet has been evaluated at different radial locations and the surface temperature increase estimated.

Gomes, R. B.; Fernandes, H.; Silva, C.; Sarakovskis, A.; Pereira, T.; Figueiredo, J.; Carvalho, B.; Soares, A.; Duarte, P.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Tale, I.

2008-04-01

205

Interaction of a Liquid Gallium Jet with ISTTOK Edge Plasmas  

SciTech Connect

The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages in the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaust from fusion devices. Presently the most promising candidate materials are lithium and gallium. However, lithium has a short liquid state range when compared, for example, with gallium that has essentially better thermal properties and lower vapor pressure. To explore further these properties, ISTTOK tokamak is being used to test the interaction of a free flying, fully formed liquid gallium jet with the plasma. The interacting, 2.3 mm diameter, jet is generated by hydrostatic pressure and has a 2.5 m/s flow velocity. The liquid metal injector has been build to allow the positioning of the jet inside the tokamak chamber, within a 13 mm range. This paper presents the first obtained experimental results concerning the liquid gallium jet-plasma interaction. A stable jet has been obtained, which was not noticeably affected by the magnetic field transients. ISTTOK has been successfully operated with the gallium jet without degradation of the discharge or a significant plasma contamination by liquid metal. This observation is supported by spectroscopic measurements showing that gallium radiation is limited to the region around the jet. Furthermore, the power deposited on the jet has been evaluated at different radial locations and the surface temperature increase estimated.

Gomes, R. B.; Fernandes, H.; Silva, C.; Pereira, T.; Figueiredo, J.; Carvalho, B.; Soares, A.; Duarte, P.; Varandas, C. [Associacao EURATOM/IST, Centro de Fusao Nuclear, Av. Rovisco Pais, 1049-001 Lisboa, Porugal (Portugal); Sarakovskis, A.; Lielausis, O.; Klyukin, A.; Platacis, E.; Tale, I. [Association EURATOM/University of Latvia, Institute of Solid State Physics, 8 Kengaraga Str., LV-1063 Riga (Latvia)

2008-04-07

206

Electronic transitions in the bandgap of copper indium gallium diselenide polycrystalline thin films  

NASA Astrophysics Data System (ADS)

The electronic properties of polycrystalline copper indium gallium diselenide thin films have been investigated, with emphasis on understanding the distribution and origin of electronic states in the bandgap. The samples studied were working photovoltaic devices with the structure ZnO/CdS/CuIn1-xGa xSe2/Mo, and photovoltaic efficiencies ranging from 8 to 16%. The CdS layer and the p-type CuIn1-xGa xSe2 film create the n+- p junction at the heart of these devices. The samples were investigated using four techniques based on the electrical response of the junction: admittance spectroscopy, drive level capacitance profiling, transient photocapacitance spectroscopy, and transient photocurrent spectroscopy. From these measurements the free carrier densities, defect densities within the bandgap, spatial uniformity, and minority carrier mobilities have been deduced. The sub-bandgap response from the CuIn1-xGaxSe2 film was dominated by two defects. One exhibited a thermal transition to the valence band with an activation energy ranging between 0.1 and 0.3 eV and thermal emission prefactors obeying the Meyer-Neldel rule. The second was detected as an optical transition 0.8 eV from the valence band edge. Neither of these defects exhibited densities that varied systematically with gallium content, implying that they are not directly connected with the group III elements in these alloys. The defect densities also do not clearly correlate with the photovoltaic device performance; however, the position of the 0.8 eV defect lies nearer to mid-gap in the higher gallium, and hence higher band gap, material. This implies that it may be a more important recombination center in these devices and may be partially responsible for the reduced photovoltaic efficiencies observed when Ga/(In + Ga) > 0.4. An additional defect response was observed near mid-gap in films grown by processes known to produce lower quality devices. The influence of defects located at grain boundaries was also investigated by comparisons with a device based on an epitaxial single crystal CuIn1-xGa xSe2 film. The grain boundaries do not appear to contain significant quantities of additional defects with sub-bandgap electronic transitions. Finally, metastabilities in the defect distributions resulting from light exposure were also explored. Understanding these metastable changes is likely to lead to a better understanding of the role of the defects in the bandgap of CuIn1-xGaxSe2 films.

Heath, Jennifer Theresa

207

Gallium-based anti-infectives: targeting microbial iron-uptake mechanisms.  

PubMed

Microbes have evolved elaborate iron-acquisition systems to sequester iron from the host environment using siderophores and heme uptake systems. Gallium(III) is structurally similar to iron(III), except that it cannot be reduced under physiological conditions, therefore gallium has the potential to serve as an iron analog, and thus an anti-microbial. Because Ga(III) can bind to virtually any complex that binds Fe(III), simple gallium salts as well as more complex siderophores and hemes are potential carriers to deliver Ga(III) to the microbes. These gallium complexes represent a new class of anti-infectives that is different in mechanism of action from conventional antibiotics. Simple gallium salts such as gallium nitrate, maltolate, and simple gallium siderophore complexes such as gallium citrate have shown good antibacterial activities. The most studied complex has been gallium citrate, which exhibits broad activity against many Gram negative bacteria at ?1-5?g/ml MICs, strong biofilm activity, low drug resistance, and efficacy in vivo. Using the structural features of specific siderophore and heme made by pathogenic bacteria and fungi, researchers have begun to evaluate new gallium complexes to target key pathogens. This review will summarize potential iron-acquisition system targets and recent research on gallium-based anti-infectives. PMID:23876838

Kelson, Andrew B; Carnevali, Maia; Truong-Le, Vu

2013-07-19

208

Multiplane gallium tomography in assessment of occupational chest diseases  

SciTech Connect

Gallium-67 scintigraphy is helpful in the evaluation of inflammatory, respiratory diseases. Single-photon emission computed tomography (SPECT) provides three-dimensional tomographic reconstruction of radioisotope distribution in the body. The addition of SPECT to gallium-67 scanning in 27 patients demonstrated an improvement in the sensitivity for detecting the presence and extent of interstitial occupational lung disease. This technique may provide earlier detection of parenchymal lung changes than can the chest x-ray and planar scanning in some patients with asbestosis. Findings in six patients with asbestosis are reported.

Cordasco, E.M.; O'Donnell, J.; MacIntyre, W.; Demeter, S.; Gonzalez, L.; Eren, M.; McMahon, W.; Burns, D.; Feiglin, D.H. (Cleveland Clinic Foundation, OH (USA))

1990-01-01

209

Room temperature lasing at blue wavelengths in gallium nitride microcavities  

PubMed

Lasing action has been demonstrated at blue wavelengths in vertical cavity surface-emitting lasers at room temperature. The microcavity was formed by sandwiching indium gallium nitride multiple quantum wells between nitride-based and oxide-based quarter-wave reflectors. Lasing action was observed at a wavelength of 399 nanometers under optical excitation and confirmed by a narrowing of the linewidth in the emission spectra from 0.8 nanometer below threshold to less than 0.1 nanometer (resolution limit) above threshold. The result suggests that practical blue vertical cavity surface-emitting lasers can be realized in gallium-nitride-based material systems. PMID:10489367

Someya; Werner; Forchel; Catalano; Cingolani; Arakawa

1999-09-17

210

On-chip superconductivity via gallium overdoping of silicon  

SciTech Connect

We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In addition, out-of-plane critical fields of above 9 T and critical current densities exceeding 2 kA/cm{sup 2} promote these structures to be possible playgrounds for future microelectronic technology.

Skrotzki, R.; Herrmannsdoerfer, T.; Heera, V.; Voelskow, M.; Muecklich, A.; Schmidt, B.; Skorupa, W.; Helm, M.; Wosnitza, J. [Dresden High Magnetic Field Laboratory (HLD) and Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf (FZD), P.O. Box 51 01 19, D-01314 Dresden (Germany); Fiedler, J. [Dresden High Magnetic Field Laboratory (HLD) and Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf (FZD), P.O. Box 51 01 19, D-01314 Dresden (Germany); Experimental Physics, Institute of Physics, Ilmenau University of Technology, Weimarer Str. 32, 98693 Ilmenau (Germany); Gobsch, G. [Experimental Physics, Institute of Physics, Ilmenau University of Technology, Weimarer Str. 32, 98693 Ilmenau (Germany)

2010-11-08

211

Gallium-67 uptake by the thyroid associated with progressive systemic sclerosis  

SciTech Connect

Although thyroidal uptake of gallium-67 has been described in several thyroid disorders, gallium-67 scanning is not commonly used in the evaluation of thyroid disease. Thyroidal gallium-67 uptake has been reported to occur frequently with subacute thyroiditis, anaplastic thyroid carcinoma, and thyroid lymphoma, and occasionally with Hashimoto's thyroiditis and follicular thyroid carcinoma. A patient is described with progressive systemic sclerosis who, while being scanned for possible active pulmonary involvement, was found incidentally to have abnormal gallium-67 uptake only in the thyroid gland. Fine needle aspiration cytology of the thyroid revealed Hashimoto's thyroiditis. Although Hashimoto's thyroiditis occurs with increased frequency in patients with progressive systemic sclerosis, thyroidal uptake of gallium-67 associated with progressive systemic sclerosis has not, to our knowledge, been previously described. Since aggressive thyroid malignancies frequently are imaged by gallium-67 scintigraphy, fine needle aspiration cytology of the thyroid often is essential in the evaluation of thyroidal gallium-67 uptake.

Sjoberg, R.J.; Blue, P.W.; Kidd, G.S.

1989-01-01

212

Method for improving the growth of cadmium telluride on a gallium arsenide substrate  

DOEpatents

A method for preparing a gallium arsenide substrate, prior to growing a layer of cadmium telluride on a support surface thereof. The preparation includes the steps of cleaning the gallium arsenide substrate and thereafter forming prepatterned shapes on the support surface of the gallium arsenide substrate. The layer of cadmium telluride then grown on the prepared substrate results in dislocation densities of approximately 1{times}10{sup 6}/cm{sup 2} or less. The prepatterned shapes on the support surface of the gallium arsenide substrate are formed by reactive ion etching an original outer surface of the gallium arsenide substrate and into the body of the gallium arsenide substrate to a depth of at least two microns. The prepatterned shapes have the appearance of cylindrical mesas each having a diameter of at lease twelve microns. After the mesas are formed on the support surface of the gallium arsenide substrate, the substrate is again cleaned.

Reno, J.L.

1990-12-31

213

Ferromagnetic shape memory alloys: structural and thermal properties  

NASA Astrophysics Data System (ADS)

The most extensively studied Heusler alloys are those based on the Ni-Mn-Ga system. However, to overcome the high cost of Gallium and the usually low martensitic transformation temperature, the search for Ga-free alloys has been recently attempted, particularly, by introducing In, Sn or Sb. In this work, two alloys (Mn50Ni35.5In14.5 and Ni50Mn35In15) have been obtained by melt spinning. We outline their structural and thermal behaviour. Mn50Ni35.5In14.5 alloy has the transformation above room temperature whereas Ni50Mn35In15 does not have this transformation in the temperature range here analyzed.

Suñol, J. J.; Escoda, L.; Coll, R.; Saurina, J.; Sánchez, T.; Prida, V. M.; Hernando, B.

2010-11-01

214

Advances in Gallium Nitride-based Electronics  

Microsoft Academic Search

The III -nitrides AIN, GaN, InN and their alloys are a novel family of semiconductor materials for optoelectronics as well as for electronics. GaN-based high electron mobility transistors (HEMTs) have shown superior power density and operating temperatures at frequency ranges that are beyond the limits of devices fabricated from Si and other III-V materials. This paper presents the advances in

I. Adesida; V. Kumar

2007-01-01

215

Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires  

SciTech Connect

Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO{sub 2} layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO{sub 2} pinholes induces the formation of nanocraters, found to be the key for the nucleation of the nanowires. With SiO{sub 2} thicknesses up to 30 nm, nanocraters reach the underlying substrate, resulting into a preferential growth orientation of the nanowires. Possibly related to the formation of nanocraters, we observe an incubation period of 258 s before the nanowires growth is initiated.

Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R. [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany); TEM-MAT, Serveis Cientificotecnics, Universitat de Barcelona, CAT, E-08080 Barcelona (Spain); EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, C/Marti i Franques 1, CAT, E-08080 Barcelona (Spain)

2008-02-11

216

Effects of electronic correlations on the mechanical properties of Gallium Phosphide using density functional theory (DFT+U)  

NASA Astrophysics Data System (ADS)

Developing an efficient material for solar energy conversion and storage has been an important task for many scientists working on renewable energy technology. Gallium phosphide (GaP) alloys are among the materials that have potential to be used in the solar technology. Hence, we investigate the elastic property, mainly the bulk modulus, and electronic properties of GaP. The goal of this work is to study the effect of electron correlation on the mechanical stability of GaP. The calculation of energy as a function of cell volume has been performed using density functional theory with U-parameter (DFT+U) The Birch-Murnaghan equation of state is used to calculate equilibrium cell volume, total energy, bulk modulus, B0, and its first pressure derivative, B0^'. The bulk modulus obtained using different U-parameter was compared with published experimental values. The use of U-parameter in Gallium d-orbital has increased the theoretical value of bulk modulus, making it closer to the experimental value. On the other hand, increasing values of U on Phosphorus p-orbital decreases the bulk modulus further. The physical consequences of these results will be discussed.

Khatri, Prashant; Butler, Brandon; Turner, John A.; Huda, Muhammad N.

2011-10-01

217

Spectroscopy of vanadium (III) doped gallium lanthanum sulphide chalcogenide glass  

Microsoft Academic Search

Vanadium doped gallium lanthanum sulphide glass (V:GLS) displays three absorption bands at 580, 730, and 1155 nm identified by photoluminescence excitation measurements. Broad photoluminescence, with a full width at half maximum of ~500 nm, is observed peaking at 1500 nm when exciting at 514, 808, and 1064 nm. The fluorescence lifetime and quantum efficiency at 300 K were measured to

M. Hughes; H. Rutt; D. Hewak; R. J. Curry

2007-01-01

218

Further measurements relating to the anisotropic thermal conductivity of gallium  

Microsoft Academic Search

Thermal conductivity determinations made over the temperature range 83° K to 293° K for three single crystal samples of the orthorhombic metal gallium having axes approximately in the crystallographic c, a and b axial directions confirm preliminary values previously obtained at about 273° K for the same samples.A method of analysis proposed by Bäcklund is used to derive the electronic

R W Powell; Margaret J Woodman; R P Tye

1963-01-01

219

Carrier recombination at dislocations in epitaxial gallium phosphide layers  

Microsoft Academic Search

The nature of dark spots observed in cathodoluminescence micrographs of gallium phosphide epitaxial layers has been examined using the transmission electron microscope and etching studies. Each dark spot is shown to be located at the intersection of a dislocation with the layer surface. Moreover screw, edge and mixed dislocations all give rise to spots of similar size and intensity. It

J. M. Titchmarsh; G. R. Booker; W. Harding; D. R. Wight

1977-01-01

220

Regenerative switching device using MBE-grown gallium arsenide  

Microsoft Academic Search

A new form of two-state switching device is proposed which is formed entirely within the semiconductor bulk during epitaxial growth. The predicted switching action is demonstrated using MBE-grown gallium arsenide and the device is shown to have optical sensitivity. The device is amenable to simple design rules and is free of the 'forming' state often associated with the tunnel MIS

C. E. C. Wood; L. F. Eastman; K. Board; K. Singer; R. Malik

1982-01-01

221

Sage: The Soviet-American gallium solar neutrino experiment  

Microsoft Academic Search

A radiochemical 71Ga-71Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Academy of Sciences of the USSR. The number of 71Ga atoms extracted from thirty tons of gallium was measured in five runs during the period of from January to July

V. N. Gavrin; O. L. Anosov; E. L. Faizov; A. V. Kalikhov; T. V. Knodel; I. I. Knyshenko; V. N. Kornoukhov; S. A. Mesentseva; I. N. Mirmov; A. V. Ostrinsky; A. M. Pshukov; N. E. Revzin; A. A. Shikhin; P. V. Timofeyev; E. P. Veretenkin; V. M. Vermul; G. T. Zatsepin; T. J. Bowles; B. T. Cleveland; S. R. Elliott; H. A. O'Brien; D. L. Wark; J. F. Wilkerson; R. Davis; K. Lande; M. L. Cherry; R. T. Kouzes

1992-01-01

222

Packaging of an iron-gallium (Galfenol) nanowire acoustic sensor  

Microsoft Academic Search

Packaging is a key issue for the effective working of an iron-gallium (Galfenol) nanowire acoustic sensor for underwater applications. The nanowire acoustic sensor incorporates cilia-like nanowires made of galfenol, a magnetostrictive material, which responds by changing magnetic flux flowing through it due to bending stress induced by the incoming acoustic waves. This stress induced change in the magnetic flux density

Rupal Jain; F. Patrick McCluskey; Alison B. Flatau; Bethanie J. H. Stadler

2007-01-01

223

Research in Gadolinium Scandium Gallium Garnet (GSGG) crystal development  

NASA Astrophysics Data System (ADS)

The Czochralski growth technique was utilized for the development of a large diameter, laser quality gadolinium, scandium gallium garnet co-doped with neodymium and chromium (Nd:Cr:GSGG). Vary aspects of the development were determinations of raw material purity, foule growth runs, boule composition and lattice parameters, and losses.

1985-07-01

224

Void formation in gallium arsenide crystals grown in microgravity  

Microsoft Academic Search

Two crystals of selenium doped gallium arsenide (SeGaAs) were grown in the crystal growth furnace (CGF), during the First United States Microgravity Laboratory (USML-1). Both of these crystals contained voids and three theories were proposed to explain the formation of these voids: (1) Evolution of dissolved argon from the liquid encapsulated Czochralski (LEC) grown crystal could have resulted in the

M. L. Kaforey; J. M. Bly; D. H. Matthiesen

1997-01-01

225

Assessment of activity of ocular sarcoidosis by gallium scanning.  

PubMed Central

Gallium (67Ga) citrate uptake over the orbits, parotid glands, and lungs was examined in six newly detected patients with sarcoidosis and 17 with chronic sarcoidosis. Six of 23 (26%) had uveitis, 18/23 (78%) decreased lacrimal secretion, and 13/16 (81%) epithelioid cell granulomas in conjunctival biopsies. Ten patients with other diseases served as controls. Only five patients had ocular complaints and two had enlarged parotid glands. 67Ga uptake over the orbits and parotids was measured by a quantitative computer based method. Gallium uptake was significantly higher over the orbits (p less than 0.001) and parotids (p less than 0.01) in the newly detected patients and in the parotids (p less than 0.01) in the chronic group than the corresponding uptake in the controls. We suggest that in sarcoidosis an increased 67Ga uptake in the orbital and parotid areas may be a phenomenon comparable to an increased 67Ga uptake in the lungs in active alveolitis. Gallium scan is a good method for revealing even symptomless ophthalmic sarcoid changes. However, in chronic sarcoidosis an equal or only slightly increased gallium uptake over the orbits compared with background activity does not exclude ocular sarcoid disease. Images

Karma, A; Poukkula, A A; Ruokonen, A O

1987-01-01

226

Laser-Induced Homoepitaxial Growth of Gallium Arsenide Films.  

National Technical Information Service (NTIS)

Epitaxial gallium arsenide films have been deposited on single crystalline GaAs substrates of (100) orientation at 425-500 C by ArF excimer laser-induced metalorganic chemical vapor deposition. The important process parameters include the cleanliness of t...

S. S. Chu T. L. Chu

1988-01-01

227

Pair distribution function study on compression of liquid gallium  

SciTech Connect

Integrating a hydrothermal diamond anvil cell (HDAC) and focused high energy x-ray beam from the superconductor wiggler X17 beamline at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL), we have successfully collected high quality total x-ray scattering data of liquid gallium. The experiments were conducted at a pressure range from 0.1GPa up to 2GPa at ambient temperature. For the first time, pair distribution functions (PDF) for liquid gallium at high pressure were derived up to 10 {angstrom}. Liquid gallium structure has been studied by x-ray absorption (Di Cicco & Filipponi, 1993; Wei et al., 2000; Comez et al., 2001), x-ray diffraction studies (Waseda & Suzuki, 1972), and molecular dynamics simulation (Tsay, 1993; Hui et al., 2002). These previous reports have focused on the 1st nearest neighbor structure, which tells us little about the atomic arrangement outside the first shell in non- crystalline materials. This study focuses on the structure of liquid gallium and the atomic structure change due to compression. The PDF results show that the observed atomic distance of the first nearest neighbor at 2.78 {angstrom} (first G(r) peak and its shoulder at the higher Q position) is consistent with previous studies by x-ray absorption (2.76 {angstrom}, Comez et al., 2001). We have also observed that the first nearest neighbor peak position did not change with pressure increasing, while the farther peaks positions in the intermediate distance range decreased with pressure increasing. This leads to a conclusion of the possible existence of 'locally rigid units' in the liquid. With the addition of reverse Monte Carlo modeling, we have observed that the coordination number in the local rigit unit increases with pressure. The bulk modulus of liquid gallium derived from the volume compression curve at ambient temperature (300K) is 12.1(6) GPa.

Luo, Shengnian [Los Alamos National Laboratory; Yu, Tony [SUNY-SB; Chen, Jiuhua [SUNY-SB; Ehm, Lars [SUNY-SB; Guo, Quanzhong [SUNY-SB; Parise, John [SUNY-SB

2008-01-01

228

Adsorption of primary substituted hydrocarbons onto solid gallium substrates.  

PubMed

Adsorption of a series of primary substituted hydrocarbons (RX; C18H37PO(OH)2 (ODPA), C17H35COOH, C18H37OH, C18H37NH2, and C18H37SH) onto solid gallium substrates with and without UV/ozone treatment was studied using contact angle goniometry, spectroscopic ellipsometry, and cyclic voltammetry (CV). UV/ozone treatment offered a hydrophilic surface (water contact angle (?(water)) less than 10°), reflecting the formation of a surface oxide layer with the maximum thickness of ca. 1 nm and possibly the removal of surface contaminants. Upon immersion in a toluene solution of a RX, ?(water) increased due to adsorption of the RX onto gallium substrates. In particular, UV/ozone-treated gallium substrates (UV-Ga) immersed in an ODPA solution exhibited ?(water) close to 105°. The ellipsometric thickness of the adsorbed ODPA layer was ca. 2.4 nm, and CV data measured in an acetonitrile solution showed significant inhibition of redox reaction on the substrate surface. These results indicate the formation of a densely packed ODPA monolayer on UV-Ga. The coverage of a C17H35COOH layer adsorbed onto UV-Ga was lower, as shown by smaller ?(water) (ca. 99°), smaller ellipsometric thickness (ca. 1.3 nm), and smaller electrode reaction inhibition. Adsorption of the other RX onto UV-Ga was weaker, as indicated by smaller ?(water) (82°-92°). ODPA did not strongly adsorb onto UV-untreated gallium substrates, suggesting that the ODPA adsorption mainly originates from hydrogen bond interaction of a phosphonate group with surface oxide. These results will provide a means for controlling the surface properties of oxide-coated gallium that play an essential role in monolayer conductivity measurements and electroanalytical applications. PMID:23484619

De Silva, Chrishani M; Pandey, Bipin; Li, Feng; Ito, Takashi

2013-03-25

229

Gallium-cladding compatibility testing plan. Phases 1 and 2: Test plan for gallium corrosion tests; Revision 2.  

National Technical Information Service (NTIS)

This test plan is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water-Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. The plan summarizes and updates the projected Phases 1 and 2 Gallium-Cladding compatibility co...

D. F. Wilson R. N. Morris

1998-01-01

230

Self- and zinc diffusion in gallium antimonide  

SciTech Connect

The technological age has in large part been driven by the applications of semiconductors, and most notably by silicon. Our lives have been thoroughly changed by devices using the broad range of semiconductor technology developed over the past forty years. Much of the technological development has its foundation in research carried out on the different semiconductors whose properties can be exploited to make transistors, lasers, and many other devices. While the technological focus has largely been on silicon, many other semiconductor systems have applications in industry and offer formidable academic challenges. Diffusion studies belong to the most basic studies in semiconductors, important from both an application as well as research standpoint. Diffusion processes govern the junctions formed for device applications. As the device dimensions are decreased and the dopant concentrations increased, keeping pace with Moore's Law, a deeper understanding of diffusion is necessary to establish and maintain the sharp dopant profiles engineered for optimal device performance. From an academic viewpoint, diffusion in semiconductors allows for the study of point defects. Very few techniques exist which allow for the extraction of as much information of their properties. This study focuses on diffusion in the semiconductor gallium antimonide (GaSb). As will become clear, this compound semiconductor proves to be a powerful one for investigating both self- and foreign atom diffusion. While the results have direct applications for work on GaSb devices, the results should also be taken in the broader context of III-V semiconductors. Results here can be compared and contrasted to results in systems such as GaAs and even GaN, indicating trends within this common group of semiconductors. The results also have direct importance for ternary and quaternary semiconductor systems used in devices such as high speed InP/GaAsSb/InP double heterojunction bipolar transistors (DHBT) [Dvorak, (2001)]. Many of the findings which will be reported here were previously published in three journal articles. Hartmut Bracht was the lead author on two articles on self-diffusion studies in GaSb [Bracht, (2001), (2000)], while this report's author was the lead author on Zn diffusion results [Nicols, (2001)]. Much of the information contained herein can be found in those articles, but a more detailed treatment is presented here.

Nicols, Samuel Piers

2002-03-26

231

Observation of persistent photoconductivity in bulk Gallium Arsenide and Gallium Phosphide samples at cryogenic temperatures using the Whispering Gallery mode method  

Microsoft Academic Search

Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at cryogenics temperatures < 50 K. In both cases persistent photoconductivity was observed after initially exposing semiconductors to white light from a halogen lamp. Photoconductance decay time constants for GaP and GaAs were determined to be 0.900 +\\/-

J. G. Hartnett; D. Mouneyrac; J.-M. Le Floch; J. Krupka; M. E. Tobar; D. Cros

2009-01-01

232

BRAZING ALLOYS  

Microsoft Academic Search

A brazing alloy which, in the molten state, is characterized by ; excellent wettability and flowability, said alloy being capable of forming a ; corrosion resistant brazed joint wherein at least one component of said joint is ; graphite and the other component is a corrosion resistant refractory metal, said ; alloy consisting essentially of 20 to 50 per cent

R. G. Donnelly; R. G. Gilliland; G. M. Slaughter

1963-01-01

233

VANADIUM ALLOYS  

Microsoft Academic Search

This patent deals with vanadium based ternary alloys useful as fuel ; element jackets. According to the invention the ternary vanadium alloys, ; prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from ; 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal ; conductivity, low neutron capture cross section, good

K. F. Smith; R. J. Van Thyne

1959-01-01

234

Gallium oxide films for filter and solar-blind UV detector  

Microsoft Academic Search

Gallium oxide thin films were deposited by pulsed spray pyrolysis in air using ethanol solution of gallium trichloride as precursor. X-ray diffraction measurements showed that monoclinic gallium oxide thin films were formed. The optical band-gap of the film deposited on quartz substrates was 5.16eV, and the transmittance was greater than 80% for ?>275nm, as determined by UV–vis absorption spectrum. Photoconductivity

Zhenguo Ji; Juan Du; Jia Fan; Wei Wang

2006-01-01

235

In Vitro and In Vivo Biological Activities of Iron Chelators and Gallium Nitrate against Acinetobacter baumannii  

PubMed Central

We investigated the ability of compounds interfering with iron metabolism to inhibit the growth of Acinetobacter baumannii. Iron restriction with transferrin or 2,2-bipyridyl significantly inhibited A. baumannii growth in vitro. Gallium nitrate alone was moderately effective at reducing A. baumannii growth but became bacteriostatic in the presence of serum or transferrin. More importantly, gallium nitrate treatment reduced lung bacterial burdens in mice. The use of gallium-based therapies shows promise for the control of multidrug-resistant A. baumannii.

Harris, Greg; KuoLee, Rhonda; Chen, Wangxue

2012-01-01

236

Gallium-cooled target for compact accelerator-based neutron sources  

Microsoft Academic Search

This paper discusses the motivation for gallium-cooling of targets of compact accelerator-based neutron sources (CANS); summarizes features of the low-power alternative, i.e., water cooling, and the limitations of boiling water heat transfer; lists the properties of liquid gallium; and cites its low hazards potential. I set out working equations for heat transport and fluid flow in liquid gallium and present

John M. Carpenter

237

Gallium uptake in the thyroid gland in amiodarone-induced hyperthyroidism  

SciTech Connect

Amiodarone is an iodinated antiarrhythmic agent that is effective in the treatment of atrial and ventricular arrhythmias. A number of side effects are seen, including pulmonary toxicity and thyroid dysfunction. A patient with both amiodarone-induced pneumonitis and hyperthyroidism who exhibited abnormal gallium activity in the lungs, as well as diffuse gallium uptake in the thyroid gland is presented. The latter has not been previously reported and supports the concept of iodide-induced thyroiditis with gallium uptake reflecting the inflammatory response.

Ling, M.C.; Dake, M.D.; Okerlund, M.D.

1988-04-01

238

Thin film gallium arsenide solar cells and crystal structure determination by X-ray diffraction  

Microsoft Academic Search

This dissertation is concerned with two parts: (1) Thin film gallium arsenide metal-oxide-semiconductor solar cells on tungsten\\/graphite substrates, and (2) Crystal structures determination of two compounds by X-ray diffraction method. The objectives of the first part are concerned with the deposition of gallium arsenide films on foreign substrates and the fabrication and characterization of thin film gallium arsenide solar cells.

H. T. Yang

1978-01-01

239

Ultraviolet light-driven epitaxial growth of gallium arsenide at reduced substrate temperatures  

Microsoft Academic Search

We report on the photodeposition of gallium arsenide on gallium arsenide and silicon at low substrate temperatures utilizing\\u000a ultraviolet radiation. A 1000 W Hg-Xe arc lamp serves as the light source with triethylgallium and arsine serving as the reactants.\\u000a In this study, single crystal gallium arsenide thin films are obtained at substrate temperatures of approximately 357. The\\u000a electrical, chemical and

D. P. Norton; P. K. Ajmera

1990-01-01

240

Cutaneous gallium uptake in patients with AIDS with mycobacterium avium-intracellulare septicemia  

SciTech Connect

Gallium imaging is increasingly being used for the early detection of complications in patients with AIDS. A 26-year-old homosexual man who was HIV antibody positive underwent gallium imaging for investigation of possible Pneumocystis carinii pneumonia. Widespread cutaneous focal uptake was seen, which was subsequently shown to be due to mycobacterium avium-intracellulare (MAI) septicemia. This case demonstrates the importance of whole body imaging rather than imaging target areas only, the utility of gallium imaging in aiding the early detection of clinically unsuspected disease, and shows a new pattern of gallium uptake in disseminated MAI infection.

Allwright, S.J.; Chapman, P.R.; Antico, V.F.; Gruenewald, S.M.

1988-07-01

241

Nonpolar m-plane gallium Nitride-based Laser Diodes in the Blue Spectrum  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN), together with its alloys with aluminum and indium, have revolutionized the solid-state optoelectronics market for their ability to emit a large portion of the visible electromagnetic spectrum from deep ultraviolet and into the infrared. GaN-based semiconductor laser diodes (LDs) with emission wavelengths in the violet, blue and green are already seeing widespread implementation in applications ranging from energy storage, lighting and displays. However, commercial GaN-based LDs use the basal c-plane orientation of the wurtzite crystal, which can suffer from large internal electric fields due to discontinuities in spontaneous and piezoelectric polarizations, limiting device performance. The nonpolar orientation of GaN benefits from the lack of polarization-induced electric field as well as enhanced gain. This dissertation discusses some of the benefits and limitations of m-plane oriented nonpolar GaN for LD applications in the true blue spectrum (450 nm). Topics include an overview of material growth by metal-organic chemical vapor deposition (MOCVD), waveguide design and processing techniques for improving device performance for multiple lateral mode and single lateral mode ridge waveguides.

Kelchner, Kathryn M.

242

Ionic Transport Studies of Anodic Gallium-Arsenide and Gallium-Arsenide Oxides.  

NASA Astrophysics Data System (ADS)

The cation and anion transport numbers for the GaAs anodic oxide were determined from Rutherford backscattering measurements of implanted ('134)Xe marker atoms. The cation transport number was found to be 0.176. These results were compared with those obtained by other researchers for anodic oxides grown on metals and semiconductors. This comparison shows that the cation transport number for GaAs is intermediate between those for metals and that for silicon. The measurements were also related to ionic transport models. Gallium arsenide cations appear to move through the process of interstitial migration. Anodization and backscattering experiments were also performed on GaAs substrates with superimposed layers of niobium, vanadium, tantalum, or aluminum. The GaAs transport numbers and oxide structures of these systems were determined for various anodization current densities and electrolyte pH values. These values were found to be slightly higher than that of the GaAs native oxide. The mixing mechanism of GaAs and Ta cations during anodization was investigated and compared with the mixing process of the Nb/Ta system. The mixing fractions for both systems were found to be nearly identical. These experiments have their primary significance in the bulk region of the anodic oxide. The implications of these results for the semiconductor-oxide interface and for the oxide-electrolyte interface are also considered.

Canaday, Jon D.

243

Preparation Of Copper Indium Gallium Diselenide Films For Solar Cells  

DOEpatents

High quality thin films of copper-indium-gallium-diselenide useful in the production of solar cells are prepared by electrodepositing at least one of the constituent metals onto a glass/Mo substrate, followed by physical vapor deposition of copper and selenium or indium and selenium to adjust the final stoichiometry of the thin film to approximately Cu(In,Ga)Se.sub.2. Using an AC voltage of 1-100 KHz in combination with a DC voltage for electrodeposition improves the morphology and growth rate of the deposited thin film. An electrodeposition solution comprising at least in part an organic solvent may be used in conjunction with an increased cathodic potential to increase the gallium content of the electrodeposited thin film.

Bhattacharya, Raghu N. (Littleton, CO); Contreras, Miguel A. (Golden, CO); Keane, James (Lakewood, CO); Tennant, Andrew L. (Denver, CO), Tuttle, John R. (Denver, CO); Ramanathan, Kannan (Lakewood, CO); Noufi, Rommel (Golden, CO)

1998-08-08

244

Gallium nitride nanowires by maskless hot phosphoric wet etching  

NASA Astrophysics Data System (ADS)

We demonstrate gallium nitride (GaN) nanowires formation by controlling the selective and anisotropic etching of N-polar GaN in hot phosphoric acid. Nanowires of ~109/cm,2 total height of ~400 nm, and diameters of 170-200 nm were obtained. These nanowires have both non-polar {1100}/ {1120} and semi-polar {1011} facets. X-Ray Diffraction characterization shows that screw dislocations are primarily responsible for preferential etching to create nanowires. Indium gallium nitride multi-quantum wells (MQWs) grown on these GaN nanowires showed a blue shift in peak emission wavelength of photoluminescence spectra, and full width at half maximum decreased relative to MQWs grown on planar N-polar GaN, respectively.

Bharrat, D.; Hosalli, A. M.; Van Den Broeck, D. M.; Samberg, J. P.; Bedair, S. M.; El-Masry, N. A.

2013-08-01

245

Corrosion of alloy 718 in a mercury thermal convection loop  

SciTech Connect

Two thermal convection loops (TCLs) fabricated from annealed alloy 718 continuously circulated mercury (Hg) with 1000 wppm gallium (Ga), respectively, for about 5000 h, duplicating previous TCL tests for annealed 316L. In each case, the maximum loop temperature was 305C, the minimum temperature was 242C, and the Hg flow rate was approximately 1.2 m/min. Unlike the 316L exposed to Hg, which above about 260C exhibited a thin, porous surface layer depleted in Ni and Cr, the alloy 718 coupons revealed essentially no wetting and, therefore, no interaction with that Hg at any temperature. Alloy 718 coupons suspended in the loops revealed inconsequentially small weight changes, and both the coupons and loop tubing exhibited no detectable metallographic evidence of attack.

Pawel, S.J.; DiStefano, J.R.; Manneschmidt, E.T.

1999-12-01

246

Properties of gallium-doped hydrogenated amorphous germanium  

Microsoft Academic Search

The effects of adding small quantities of gallium atoms to hydrogenated amorphous germanium (a-Ge:H) on its dark-conductivity, band-gap, electronic density of states and the hydrogen bonding, were studied in detail by dark-conductivity, optical and infrared-transmission, and photothermal-deflection-spectroscopy measurements. Films of a-Ge:H having relative Ga atomic concentrations ranging between 3×10-5 and 1×10-2 were deposited by the cosputtering of solid Ge and

D. Comedi; F. Fajardo; I. Chambouleyron

1995-01-01

247

Sol-gel synthesis and characterization of yttrium gallium garnets  

Microsoft Academic Search

Precursor powders for yttrium gallium garnet (Y3Ga5O12, YGG) were prepared by a simple sol-gel method based on the formation of metal chelates in aqueous solvents. A systematic study of sol-gel technique synthesized YGG samples is presented using different complexing agents. Six high-purity organic substances were used as complexing agents, namely, tartaric acid, 1,2-ethanediol, citric acid, ethylene diamine tetra-acetic acid (EDTA),

Asta Leleckaite; Sigita Urbonaite; Kaia Tõnsuaadu; Aivaras Kareiva

2005-01-01

248

Faraday rotation in single-crystal ytterbium gallium garnet  

Microsoft Academic Search

Faraday rotation (FR) measurements performed on single-crystal ytterbium gallium garnet (YbGG) at 0.6328- and 1.15-?m wavelengths are presented in a magnetic field up to 20 kOe applied along the three main crystallographic directions and in the 6–300 K temperature range. At 0.6328 ?m, the FR is proportional to the magnetic field and a strong anisotropy of the Verdet constant (V)

M. Guillot; H. Le Gall; J. Ostorero; M. Artinian; A. Marchand

1987-01-01

249

Energy levels of nitrogen-nitrogen pairs in gallium phosphide  

Microsoft Academic Search

It is proposed that the line spectrum of nitrogen-nitrogen pairs in gallium phosphide arises from the recombination of an exciton situated at one nitrogen atom, its energy being perturbed by the strain field of a second nitrogen atom. The model predicts a series of lines with energies displaced from a series limit by an amount ?prime?NN-3, with ?prime a constant

J W Allen

1968-01-01

250

Synthesis and optical properties of gallium phosphide nanotubes.  

PubMed

Gallium phosphide nanotubes with zinc blende structure were synthesized for the first time. The as-prepared GaP nanotubes are polycrystalline with diameters of 30-120 nm and occasionally partially filled. The growth has been reasonably proposed to follow vapor-liquid-solid (VLS) mechanism. The integration of the nanotubular structure with the unique intrinsic semiconducting properties of GaP might bring GaP nanotubes some novel optical and electronic properties and applications. PMID:16853550

Wu, Qiang; Hu, Zheng; Liu, Chun; Wang, Xizhang; Chen, Yi; Lu, Yinong

2005-10-27

251

Gallium phosphide photonic crystal nanocavities in the visible  

Microsoft Academic Search

Photonic crystal nanocavities at visible wavelengths are fabricated in a high refractive index (n>3.2) gallium phosphide membrane. The cavities are probed via a cross-polarized reflectivity measurement and show resonances at wavelengths as low as 645 nm at room temperature, with quality factors between 500 and 1700 for modes with volumes 0.7(lambda\\/n)3. These structures could be employed for submicron scale optoelectronic

Kelley Rivoire; Andrei Faraon; Jelena Vuckovic

2008-01-01

252

Gallium phosphide monolithic display with low drive power  

Microsoft Academic Search

A gallium phosphide monolithic numeric display with seven segments has been developed by a mesa-etching technique. Internal absorption of red emission is small so that optical isolation is very difficult in monolithic-type displays. This obstacle has been overcome by sufficiently deep mesa-etching in hot aqua regia, using a stable SiO2film as a mask. Luminance and optical isolation of segments are

AKINOBU KASAMI; MAKOTO NAITO; MASAHARU TOYAMA

1972-01-01

253

Flatband Electroreflectance of Gallium Arsenide. I. Experimental Results  

Microsoft Academic Search

The electroreflectance (ER) spectrum of n-type gallium arsenide in the 1. 2-5. 3-eV photon energy range has been measured. It was found from examination of the direct-edge Delta?1 line shapes and collaborative differential capacitance measurements that quite uniform fields were obtained. The interference between the light- and heavy-hole contributions to the ER signal at E0 was observed. The data were

Stephen F. Pond; Paul Handler

1972-01-01

254

A gallium phosphide high-temperature bipolar junction transistor  

Microsoft Academic Search

Preliminary results are reported on the development of a high-temperature (> 350°C) gallium phosphide bipolar junction transistor (BJT) for goethermal and other energy applications. This four-layer p\\/sup +\\/n⁻pp\\/sup +\\/ structure was fromed by liquid phase epitaxy using a supercooling technique to insure uniform nucleation of the thin layers. Magnesium was used as the p-type dopant to avoid excessive out-diffusion into

T. E. Zipperian; L. R. Dawson; R. J. Caffin

1981-01-01

255

Surfactant Modified Nickel-Manganese-Gallium Powder and Silicone Composites  

Microsoft Academic Search

Power supplies are often the limiting factor for operation of many portable electronic devices. Batteries contribute significantly to their weight and impose limitations on operational longevity. Harvesting vibratory energy from the environment for conversion to electrical energy has been proposed as a means to address these problems. Previously, DRDC Atlantic has shown that single crystals of nickel-manganese-gallium (NiMnGa) can produce

Royale S. Underhill; Krystal A. Stevens; Gary C. Fisher

2008-01-01

256

Diagnosis of mycotic abdominal aortic aneurysm using 67-gallium citrate  

SciTech Connect

Mycotic aneurysms of the abdominal aorta are uncommon, but potentially lethal problems. Clinical subtleties may suggest their presence, but in the past, definitive diagnosis has been dependent on surgical exploration or autopsy findings. A case is presented in which 67-gallium citrate abdominal scanning localized the site of sepsis in an abdominal aortic aneurysm and allowed for prompt and successful surgical therapy. This noninvasive technique is recommended as a adjunct in the diagnosis of mycotic abdominal aortic aneurysms.

Blumoff, R.L.; McCartney, W.; Jaques, P.; Johnson, G. Jr.

1982-11-01

257

Intrinsic noise characteristics of gallium nitride high electron mobility transistors  

Microsoft Academic Search

Wide bandgap gallium nitride high electron mobility transistors (GaN HEMTs) have recently been developed for microwave sources and amplifiers. An experimental and numerical modeling effort is presented to study noise mechanisms within GaN HEMTs. This allows an equivalent-circuit model to be established, facilitating the extraction of intrinsic noise and also microwave circuit design. ^ Intrinsic noise sources in GaN HEMTs

Sungjae Lee

2004-01-01

258

Fabrication and characterization of gallium nitride electronic devices  

Microsoft Academic Search

Gallium nitride (GaN)-based high electron mobility transistors (HEMTs), metal oxide semiconductor field effect transistors (MOSFETs), and Schottky rectifiers were fabricated and characterized. Novel dielectric materials Gd 2O3 and ScO were evaluated as potential gate dielectrics for GaN MOS applications. The devices presented herein show tremendous potential for elevated temperature, high frequency, and\\/or high voltage operation. AlGaN\\/GaN HEMTs were grown by

Jerry Wayne Johnson

2001-01-01

259

Gallium nitride based electronics and opto-electronics  

Microsoft Academic Search

The benefit provided by optoelectronic applications of gallium nitride is immeasurable and, contrary to electronics applications, it provides an unique solution not merely a better one. This is because of the wide range of tunable and direct band gaps available in the (Al,Ga,In)N family from the deep UV (AlN; 6.2 eV) to values commensurate with metals when including the mixed

Umesh K. Mishra; Steven P. DenBaars

1998-01-01

260

Metrology of gallium nitride electronics using micro-Raman spectroscopy  

Microsoft Academic Search

Possessing a wide band gap and large break down field, gallium nitride (GaN) is of interest for a host of high power, high frequency applications including next generation cellular base stations, advanced military radar, and WiMAX networks. Much of this interest stems from the continued development of the AlGaN\\/GaN high electron mobility transistor (HEMT) that is capable of operating at

Thomas E. Beechem III

2008-01-01

261

40 W Gallium-Nitride Microwave Doherty Power Amplifier  

Microsoft Academic Search

This paper presents a 40 W gallium-nitride microwave Doherty power amplifier for WCDMA repeater applications. The main and peaking amplifier are implemented using two 20 W PEP GaN HEMTs. Its performance is evaluated for broadband gain, power efficiency and adjacent-channel-power-ratio (ACPR). The experimental results of the GaN Doherty amplifier yielded a power gain over 11 dB from 1.8 GHz to

Kyoung-Joon Cho; Wan-Jong Kim; Jong-Heon Kim; S. P. Stapleton

2006-01-01

262

Use of Gallium-67 in the diagnosis of occult infections  

SciTech Connect

The mechanism of Ga-67 citrates in the diagnosis of infection involves the rapid binding of gallium by transferrin. The Ga-67-transferrin complex gains access into inflammatory tissue to some extent through the leaky endothelium of vessels at sites of inflammation. In addition, Ga-67 binds to a limited extent to circulating neutrophils. Advances in imaging techniques using Ga-67 citrates are discussed. The clinical applications include the diagnosis of bone and joint infections, pulmonary lesions, and infections of the urinary tract.

Hoffer, P.B.

1981-05-01

263

Radiation-induced metastable ordered phase in gallium nitride  

SciTech Connect

Energetic particle irradiation is one of the useful ways for realizing metastable phases far from the equilibrium state. In the present study, we performed electron-beam-irradiation into gallium nitride (GaN) with a wurtzite structure and examined its structural changes using transmission electron microscopy. It was found that superlattice Bragg reflections appear in the electron diffraction patterns of the irradiated GaN. This suggests that the wurtzite GaN transforms to another crystalline structure with atomic ordering.

Ishimaru, Manabu [Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047 (Japan)

2010-05-10

264

Appraisal of lupus nephritis by renal imaging with gallium-67  

SciTech Connect

To assess the activity of lupus nephritis, 43 patients with systemic lupus erythematosus (SLE) were studied by gallium imaging. Delayed renal visualization 48 hours after the gallium injection, a positive result, was noted in 25 of 48 scans. Active renal disease was defined by the presence of hematuria, pyuria (10 or more red blood cells or white blood cells per high-power field), proteinuria (1 g or more per 24 hours), a rising serum creatinine level, or a recent biopsy specimen showing proliferative and/or necrotizing lesions involving more than 20 percent of glomeruli. Renal disease was active in 18 instances, inactive in 23, and undetermined in seven (a total of 48 scans). Sixteen of the 18 scans (89 percent) in patients with active renal disease showed positive findings, as compared with only four of 23 scans (17 percent) in patients with inactive renal disease (p less than 0.001). Patients with positive scanning results had a higher rate of hypertension (p = 0.02), nephrotic proteinuria (p = 0.01), and progressive renal failure (p = 0.02). Mild mesangial nephritis (World Health Organization classes I and II) was noted only in the patients with negative scanning results (p = 0.02) who, however, showed a higher incidence of severe extrarenal SLE (p = 0.04). It is concluded that gallium imaging is a useful tool in evaluating the activity of lupus nephritis.

Bakir, A.A.; Lopez-Majano, V.; Hryhorczuk, D.O.; Rhee, H.L.; Dunea, G.

1985-08-01

265

Collective fabrication of gallium-arsenide-based microsystems  

NASA Astrophysics Data System (ADS)

GaAs is for many people regarded as being too difficult and expensive for a sensor or actuator application. It is a fact that GaAs is not cheap in comparison with silicon and also cannot currently be produced with as high purity and few crystalline defects as Si. Therefore, it is preferable to use GaAs where and when one can take advantage of the good properties that it possesses. Possible applications could be where high working-temperature, high frequency, integrated optoelectronics or piezoelectricity are demanded. As for silicon, gallium arsenide based microsystems should be manufactured on industrial production lines, with an additional post-processing for microsystem specific structures. Thus, using the same approach applied to silicon, CMP investigates gallium arsenide micromachining techniques using the Philips Microwave Limeil HEMT and the Vitesse MESFET foundry processes. This paper treats the advantages and disadvantages of gallium arsenide as a micromechanical material in comparison with silicon and quartz. The MESFET and HEMT compatible micromachining will also be detailed.

Karam, Jean-Michel; Courtois, Bernard; Holjo, M.; Leclercq, J. L.; Viktorovitch, P.

1996-09-01

266

Incidental diagnosis of pregnancy on bone and gallium scintigraphy  

SciTech Connect

Bone and gallium scintigraphy were performed as part of the diagnostic workup of a 21-yr-old woman who presented at our institution with a history of progressively worsening low back pain over a 1-wk period of time. The angiographic phase of the bone scan demonstrated a well-defined radionuclide blush within the pelvis just cephalad to the urinary bladder with persistent hyperemia noted in the blood-pool image. We attribute these findings to a uterine blush secondary to the pronounced uterine muscular hyperplasia, hyperemia, and edema that accompany pregnancy. Gallium scintigraphy demonstrated intense bilateral breast accumulation of the imaging agent in a typical doughnut pattern which is commonly found in the prelactating and lactating breast. Also demonstrated was apparent gallium accumulation in the placenta. This case is presented to emphasize the radionuclide findings that occur during pregnancy, particularly the incidental finding of radionuclide blush during the angiographic phase of a radionuclide scintigraphy which should alert the nuclear physician to the possibility of pregnancy in a woman of childbearing age.

Palestro, C.J.; Malat, J.; Collica, C.J.; Richman, A.H.

1986-03-01

267

Micromilling of metal alloys with focused ion beam–fabricated tools  

Microsoft Academic Search

This work combines focused ion beam sputtering and ultra-precision machining as a first step in fabricating metal alloy microcomponents. Micro-end mills having ?25 ?m diameters are made by sputtering cobalt M42 high-speed steel and C2 micrograin tungsten carbide tool blanks. A 20 keV focused gallium ion beam is used to define a number of cutting edges and tool end clearance.

David P. Adams; Michael J. Vasile; Gilbert Benavides; Ann N. Campbell

2001-01-01

268

Micromilling of Metal Alloys with Focused Ion Beam-Fabricated Tools  

Microsoft Academic Search

This work combines focused ion beam sputtering and ultra-precision machining as a first step in fabricating microstructure in metals and alloys. Specifically, â25μm diameter micro-end mills are made from cobalt M42 high-speed steel and C2 micrograin tungsten carbide tool blanks by ion beam sputtering. A 20 keV focused gallium beam defines tool cutting edges having radii of curvature < 0.1μm.

DAVID P. ADAMS; M. J. VASILE; GILBERT L. BENAVIDES; ANN N. CAMPBELL

1999-01-01

269

Galvanic corrosion behavior of titanium implants coupled to dental alloys.  

PubMed

The corrosion of five materials for implant suprastructures (cast-titanium, machined-titanium, gold alloy, silver-palladium alloy and chromium-nickel alloy), was investigated in vitro, the materials being galvanically coupled to a titanium implant. Various electrochemical parameters E(CORR), i(CORR) Evans diagrams, polarization resistance and Tafel slopes) were analyzed. The microstructure of the different dental materials was observed before and after corrosion processes by optical and electron microscopy. Besides, the metallic ions released in the saliva environment were quantified during the corrosion process by means of inductively coupled plasma-mass spectrometry technique (ICP-MS). The cast and machined titanium had the most passive current density at a given potential and chromium-nickel alloy had the most active critical current density values. The high gold content alloys have excellent resistance corrosion, although this decreases when the gold content is lower in the alloy. The palladium alloy had a low critical current density due to the presence of gallium in this composition but a selective dissolution of copper-rich phases was observed through energy dispersive X-ray analysis. PMID:15348025

Cortada, M; Giner, L; Costa, S; Gil, F J; Rodríguez, D; Planell, J A

2000-05-01

270

Ion implantation of indium gallium arsenide  

NASA Astrophysics Data System (ADS)

The ternary compound In0.53Ga0.47As, lattice-matched to Inp, is a semiconductor alloy of technological importance for numerous electronic and optoelectronic device applications. One of these applications includes photodiodes to be developed for the 1.3--1.55 mum wavelength range where silica fibers have their lowest optical loss. With a rapid increase in its use there is an essential need to understand the effects of ion implantation of this alloy semiconductor for implant isolation purposes in which highly resistive layers are required. Due to the small band gap (0.75 eV at 300K) of In0.53Ga0.47As, the estimated maximum resistivity is of the order of 1000 O-cm. Implant isolation can be achieved by the implantation of either inert noble gas ions or electrically active ions. Ion bombardment with inert species introduces defects which trap charge carriers. In the case of implant isolation by electrically active ions, the implanted impurities form an electronic level located close to the middle of the bandgap. Studies of the effects of implantation in In0.53Ga0.47 As due to damage by implantation of Ne+ ions and to compensation by implantation of Fe+ ions are reported in this thesis. The former only involves lattice damage related effects while the latter leads to damage and dopant induced compensation. From the Ne+ implantation results it appears that the damage related energy levels in In0.53 Ga0.47M produced by ion bombardment of chemically inactive species, are not sufficiently deep to lead to effective isolation. A higher resistivity of the order of 770 O-cm is achieved with Fe+ implantation, indicating that Fe introduces an energy level deep in the bandgap. The changes in the electrical properties of the layers are correlated to the lattice damage (damage induced effects) and/or the diffusion of the compensating dopants (dopant induced compensation). Structural characterization of the layers is performed with channeling Rutherford Backscattering Spectrometry (RBS). The distribution of the compensating dopants in the as-implanted and annealed layers is examined by Secondary Ion Mass Spectrometry (SIMS). SIMS analysis shows Fe out-diffusion which results in the loss of the semi-insulating electrical characteristics. To further our understanding of Fe diffusion in In0.53Ga0.47As, the diffusion coefficient of Fe is measured for the first time. The diffusivity of Fe was measured to be 4 x 10-13 cm2 s-1 at 550°C. The thermal stability of these damage and compensation induced effects producing implant isolation is discussed in detail.

Almonte, Marlene Isabel

271

Gallium(III) does not actively substitute for iron(III) in iron\\/gallium competition studies  

Microsoft Academic Search

Strategy II plants respond to Fe stress by releasing a phytosiderophore and are believed to absorb Fe as Fe(III). Gallium(III) has chemical characteristics which have made it useful as a substitute for Fe(III) in biological systems. The objectives of our study were to: 1) determine if Ga(III) acts competitively to reduce Fe(III) uptake or otherwise substitutes for Fe(III) in barley

Michael J. Biaylock; Von D. Jolley; John C. Brown

1989-01-01

272

Heusler alloys  

Microsoft Academic Search

In 1903 F. Heusler reported that it was possible to make ferromagnetic alloys from non-ferromagnetic constituents copper-manganese bronze and group B elements such as aluminium and tin. Further investigations showed that the magnetic properties of these alloys are related to their chemical, L21, structure, and to the ordering of the manganese atoms on an f.c.c. sublattice.Heusler alloys are properly described

Peter J. Webster

1969-01-01

273

BRAZING ALLOYS  

DOEpatents

A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

1963-02-26

274

EXTRACTION OF GALLIUM\\/III\\/ FROM HYDROCHLORIC ACID BY DIISOPROPYL ETHER AND MIXTURE DIISOPROPYL ETHER-PENTANOL  

Microsoft Academic Search

In systems containing gallium (III) and hydrochloric acid, extraction with pure IPE and a mixture of IPE - pentanol was studied. The influence of the initial concentration of acid and the solvent composition as well as the temperature on the extraction of the gallium and the equilibrated phase volumes was examined. The synergistic extraction of gallium (III)was found with a

Du. Maljkovic; Da. Maljkovid; A. Paulin

1990-01-01

275

Zintl cluster chemistry in the alkali-metal-gallium systems  

SciTech Connect

Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs{sub 8}Ga{sub 11}. The geometry of the Ga{sub 11}{sup 7{minus}} unit is not deltahedral but can be described as a penta-capped trigonal prism. The reduction of the charge from a closo-Ga{sub 11}{sup 13{minus}} to Ga{sub 11}{sup 7{minus}} is believed to be the driving force of the distortion. The compound is paramagnetic because of an extra electron but incorporation of a halide atom into the structure captures the unpaired electron and forms a diamagnetic compound. A second isolated cluster has been found in Na{sub 10}Ga{sub 10}Ni where the tetra-capped trigonal prismatic gallium is centered by nickel. Stabilization of the cluster occurs through Ni-Ga bonding. A simple two-dimensional network occurs in the binary K{sub 2}Ga{sub 3} Octahedra are connected through four waist atoms to form a layered structure with the potassium atoms sitting between the layers. Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x} is nonstoichiometric and needs only a small amount of silver to form (x {approximately} 2--6). The structure is composed of three different clusters which are interconnected to form a three-dimensional structure. The RbGa{sub 3{minus}x}Au{sub x} system is also nonstoichiometric with a three-dimensional structure composed of Ga{sub 8} dodecahedra and four-bonded gallium atoms. Unlike Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x}, the RbGa{sub 3} binary is also stable. The binary is formally a Zintl phase but the ternary is not. Some chemistry in the alkali-metal-indium system also has been explored. A new potassium-indium binary is discussed but the structure has not been completely characterized.

Henning, R.

1998-03-27

276

Properties of Closed-Shell Titanium Silicate and Gallium-Containing Semiconductor Systems  

NASA Astrophysics Data System (ADS)

We demonstrate that an atomic-scale approach may be appropriate for the analysis of the compositional and bonding properties of titanium silicate alloys and shallow d-core level reflectance spectra of gallium-compound semiconductors. Ti silicate analysis was conducted using X-Ray Absorption Spectroscopy (XAS), X-Ray Photoemission Spectroscopy (XPS), and Spectroscopic Ellipsometry (SE) data taken on a range of Ti-silicate alloys. XAS data were obtained by the Lucovsky group at Stanford Synchrotron Radiation Laboratories (SSRL) at the Stanford Linear Accelerator Center (SLAC), and were used as the primary source of information. To bolster conclusions we solicited XPS data from the Opila Laboratory at the University of Delaware, which were provided by Les Fleming. We also took SE data on Ti silicate alloys annealed at different temperatures using two ellipsometers, one of which was built by the author specifically to probe energies in the vacuum uv range. Reflectance data from 20 to 25 eV, which contain spectral features due to transitions from Ga3d core levels, were obtained on GaP, GaAs, GaSb, GaSe, and GaPxAs1ƒ{x at the storage ring Tantalus 1 at the Stoughton Synchrotron Radiation Center by Aspnes and co-workers from about 1980 to 1982. Ti L2,3 XAS data were fitted with reference spectra to obtain 4-fold coordination concentrations (in differing symmetries) and 6-fold coordination concentrations with respect to alloy composition and annealing. Analyzing the concentrations allowed us to draw conclusions on coordination with respect to alloy composition and annealing. We were able to model the 4-fold ¡§in solution¡¨ to 6-fold phase-segregated conversion as a stochastic process, and we found a complete conversion to 6-fold phase-segregated TiO 2 through annealing with at least 36% Ti and above. We attributed this phase segregation to a striation effect previously reported in the literature. XAS OK1 spectra corroborate these results. Investigation of the XPS Ti L 2,3 data verified the formal Ti valence in the Ti silicate alloys as +4. Through atomic-multiplet calculations, we show that because of Coulombic and spin orbit effects the final states of the Ti L2,3 spectra do not maintain any significant degeneracy, even in the absence of a crystal field. Dielectric functions from 1.5 to 9.0 eV, extracted from the SE data obtained on annealed Ti silicate alloys, verified that significant coordination change occurred between the annealing temperature of 500 and 700 °C. A local atomic multiplet theory was applied to investigate the Ga3d shallow core-level spectra of GaP, GaAs, GaSb, GaSe, and GaAs1-xP x. This is a novel application of an existing theory that is typically used for higher-energy transitions. We modeled these spectra quantitatively as a Ga+3 closed-shell ion affected by perturbations on 3d hole-4p electron final states, specifically spin-orbit effects on the hole and electron, and a crystal-field effect on the hole. The crystal-field perturbation arises from the surrounding bond charges and positive ligand anions. Radial-strength parameters were obtained through a least-squares process, and general trends identified with respect to anion electronegativity. Primary conclusion drawn is that the crystal-field effect, in addition to the spin-orbit interaction, plays a significant role in breaking d-level degeneracy, and consequently is necessary to understand shallow 3d core level spectra.

Stoute, Nicholas Aaron

277

Spintronics: Towards room temperature ferromagnetic devices via manganese and rare earth doped gallium nitride  

NASA Astrophysics Data System (ADS)

Spintronics is a multidisciplinary field aimed at the active manipulation of spin degrees of freedom in solid-state systems. The goal being the understanding of the interaction between the particle spin and its solid-state environment, and the making of useful devices based on the acquired knowledge. If Moore's law is to continue, then we need to find alternatives to conventional microelectronics. Where conventional electronic devices rely on manipulating charge to produce desired functions, spintronic devices would manipulate both the charge flow and electron spin within that flow. This would add an extra degree of freedom to microelectronics and usher in the era of truly nanoelectronic devices. Research aimed at a whole new generation of electronic devices is underway by introducing electron spin as a new or additional physical variable, and semiconductor devices that exploit this new freedom will operate faster and more efficiently than conventional microelectronic devices and offer new functionality that promises to revolutionize the electronics industry. Long recognized as the material of choice for next-generation solid-state lighting, gallium nitride (GaN) also has proven uses in the field of high power, high frequency field-effect transistors (FETs). But its promise as a material system for spintronic applications may be its ultimate legacy. In this dissertation, the growth of gallium-manganese-nitride (GaMnN) compound semiconductor alloy was investigated through the use of an in-house built metal-organic chemical vapor deposition (MOCVD) reactor. Building on previous investigations of ferromagnetic mechanisms in GaMnN, where ferromagnetism was shown to be carrier mediated, a above room temperature ferromagnetic GaMnN i-p-n diode structure was conceived. This device proved to be the first of its kind in the world, where ferromagnetic properties are controlled via proximity of the mediating holes, upon voltage bias of adjacent structure layers. Simultaneously, post-growth diffusion of ferromagnetic, rare earth species into GaN template thin films also was investigated. Structural, electrical, optical and magnetic characterization of diffused films grown on sapphire was performed. Optimization of the conditions leading to the first successful diffusion of neodymium into GaN thin films, and the magnetic and optical studies that followed are detailed. A mechanism governing and conditions promoting ferromagnetism in rare earth (RE) doped GaN is proposed. The magnetic relationship between two similar and dissimilar rare earth elements, in a single GaN crystal are investigated. Finally, spin valve and magnetic tunnel junction devices based on the magnetic properties of RE-GaN thin films are investigated.

Luen, Melvyn Oliver

278

Bit-Systolic Arithmetic Arrays Using Dynamic Differential Gallium Arsenide Circuits.  

National Technical Information Service (NTIS)

A new family of gallium arsenide circuits for fine grained bit-systolic arithmetic arrays is introduced. This scheme combines features of two recent techniques of dynamic gallium arsenide FET logic and differential dynamic single-clock CMOS logic. The res...

G. Beagles K. Winters A. G. Eldin

1992-01-01

279

The distribution of nickel, cobalt, gallium, palladium and gold in iron meteorites  

Microsoft Academic Search

The concentrations of nickel, cobalt, gallium, palladium and gold have been determined in 45 iron meteorites including representatives from all structural classes. Gallium was determined, in addition, in two specimens of troilite and in the metallic phase of two pallasites. The analytical procedures and the structural characteristics of the meteorites studied are described in detail. It is found that most

Edward Goldberg; Aiji Uchiyama; Harrison Brown

1952-01-01

280

Determination of the Peltier coefficient for gallium arsenide in a vertical Bridgman furnace  

Microsoft Academic Search

The Peltier coefficient for gallium arsenide solid in contact with its melt was experimentally determined. Selenium doped gallium arsenide samples were hermetically sealed in a fused quartz ampoule and processed in a vertical Bridgman furnace. During the translation period seven sequences of current-on and current-off periods were processed into the solidifying crystal. An axial slice was mechanochemically polished and then

Michaela E. K. Wiegel; David H. Matthiesen

2011-01-01

281

Kinetics and growth mechanism of gallium arsenide crystals in gas-phase epitaxy  

Microsoft Academic Search

In conclusion, we note that gallium arsenide itself is the material with which the physicochemical and crystallophysical fundamentals of gas-phase epitaxy are presently being developed. It is hoped that the basic principles or crystal growth in gas-phase systems discovered in gallium arsenide will prove sufficiently general to be applied to other analogous systems.

L. G. Lavrent'eva

1980-01-01

282

The incorporation of erbium into molecular beam epitaxy grown gallium arsenide  

Microsoft Academic Search

Erbium-doped gallium arsenide has been grown by molecular beam epitaxy under varying growth conditions and analysed by secondary ion mass spectrometry. The concentration of erbium incorporated into the gallium arsenide lattice for a given effusion cell temperature has been found to vary considerably with the V : III (As : Ga) flux ratio. Higher levels of erbium incorporation occur when

P. Rutter; K. E. Singer; A. R. Peaker

1997-01-01

283

A simple system for multiwafer large area, thick film growth of cadmium telluride on gallium arsenide  

Microsoft Academic Search

A simple multiwafer UHV evaporator has been developed for the large area epitaxial growth of cadmium telluride onto gallium arsenide substrates. Studies have been made of the effect of substrate temperature on the layer crystallography and the degree of gallium interdiffusion from the substrate for both the (111) and (100) faces. In the case of the (111) face it was

D. C. Rodway

1992-01-01

284

Current density dependence of minimum noise figure for gallium nitride HEMTs  

Microsoft Academic Search

This paper discusses recent work in noise characterization of gallium nitride high electron mobility transistors (HEMTs). The excellent noise performance of gallium nitride-based HEMTs has been discussed previously in the scientific literature. In this paper, we discuss observations that show that the best minimum noise figure is found at a constant current density, regardless of the physical dimensions of the

Tyler Ross; Gabriel Cormier; Khelifa Hettak; Rony E. Amaya

2010-01-01

285

Bone and gallium scanning in the pre-op evaluation of the infected dysvascular foot  

Microsoft Academic Search

The purpose of this study is to determine the value of bone and gallium scans in predicting healing levels in the dysvascular foot with an infection requiring amputation. Healing requires amputation at a level both free of infection and with adequate blood flow. Forty-one such patients had bone and gallium scans and Doppler studies prior to amputation at a level

C. Stewart; I. Sakimura; A. Dillon; M. E. Siegel

1984-01-01

286

Failure of Gallium-67 scintigraphy to identify reliably noninfectious interstitial nephritis: concise communication  

SciTech Connect

Gallium-67 scintigraphy has been reported to be useful in the diagnosis of noninfectious interstitial nephritis. We studied 12 patients with Ga-67 citrate that were diagnosed as having noninfectious interstitial nephritis on renal biopsy. Only seven of the twelve patients with interstitial nephritis on biopsy were scan-positive. Gallium-67 scintigraphy may not reliably identify noninfectious interstitial nephritis.

Graham, G.D.; Lundy, M.M.; Moreno, A.J.

1983-07-01

287

Synthesis and use of (polyfluoroaryl)fluoroanions of aluminum, gallium and indium  

DOEpatents

Salts of (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are described. The (polyfluoroaryl)fluoroanions have the formula [ER'R"R'"F].sup..crclbar. wherein E is aluminum, gallium, or indium, wherein F is fluorine, and wherein R', R", and R'" is each a fluorinated phenyl, fluorinated biphenyl, or fluorinated polycyclic group.

Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Midland, MI)

2000-01-01

288

Siderophore-mediated mechanism of gallium uptake demonstrated in the microorganism Ustilago sphaerogena  

SciTech Connect

The radioactive gallium analog of ferrichrome, Ga-67 deferriferrichrome, has been prepared and compared with ferrichrome in the specific siderophore-transport system of Ustilago sphaerogena. The gallium analog is taken up by the cells in an active transport process indistinguishable from that of ferrichrome. The findings may explain how Ga(III) mimics Fe(III) in clinical use.

Emery, T. (Utah State Univ., Logan); Hoffer, P.B.

1980-10-01

289

Gallium uptake in the thyroid gland in amiodarone-induced hyperthyroidism  

Microsoft Academic Search

Amiodarone is an iodinated antiarrhythmic agent that is effective in the treatment of atrial and ventricular arrhythmias. A number of side effects are seen, including pulmonary toxicity and thyroid dysfunction. A patient with both amiodarone-induced pneumonitis and hyperthyroidism who exhibited abnormal gallium activity in the lungs, as well as diffuse gallium uptake in the thyroid gland is presented. The latter

M. C. Ling; M. D. Dake; M. D. Okerlund

1988-01-01

290

Nonswelling alloy  

DOEpatents

An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

Harkness, S.D.

1975-12-23

291

BRAZING ALLOYS  

Microsoft Academic Search

A brazing alloy is described which, in the molten state, is ; characterized by excellent wettability and flowability and is capable of forming ; a corrosion-resistant brazed joint. At least one component of said joint is ; graphite and the other component is a corrosion-resistant refractory metal. The ; brazing alloy consists essentially of 40 to 90 wt % of

R. G. Donnelly; R. G. Gilliland; G. M. Slaughter

1962-01-01

292

URANIUM ALLOYS  

DOEpatents

Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

Seybolt, A.U.

1958-04-15

293

Measurement of achievable plutonium decontamination from gallium by means of PUREX solvent extraction  

SciTech Connect

The objective of the work described herein was to measure, experimentally, the achievable decontamination of plutonium from gallium by means of the PUREX solvent extraction process. Gallium is present in surplus weapons-grade plutonium (WG-Pu) at a concentration of approximately 1 wt%. Plans are to dispose of surplus WG-Pu by converting it to UO{sub 2}-PuO{sub 2} mixed oxide (MOX) fuel and irradiating it in commercial power reactors. However, the presence of high concentrations of gallium in plutonium is a potential corrosion problem during the process of MOX fuel irradiation. The batch experiments performed in this study were designed to measure the capability of the PUREX solvent extraction process to separate gallium from plutonium under idealized conditions. Radioactive tracing of the gallium with {sup 72}Ga enabled the accurate measurement of low concentrations of extractable gallium. The experiments approximated the proposed flowsheet for WG-Pu purification, except that only one stage was used for each process: extraction, scrubbing, and stripping. With realistic multistage countercurrent systems, much more efficient separations are generally obtained. The gallium decontamination factor (DF) obtained after one extraction stage was about 3 x 10{sup 6}. After one scrub stage, all gallium measurements were less than the detection limit, which corresponded to DFs >5 x 10{sup 6}. All these values exceed a 10{sup 6} DF needed to meet a hypothetical 10-ppb gallium impurity limit in MOX fuel. The results of this study showed no inherent or fundamental problem with regard to removing gallium from plutonium.

Collins, E.D.; Campbell, D.O.; Felker, L.K.

2000-01-01

294

The physics and modeling of gallium arsenide solar cells  

SciTech Connect

Gallium arsenide is a versatile semiconductor used in many devices. Due to its nearly ideal bandgap energy for solar energy conversion and its compatibility with AlGaAs, gallium arsenide's use in solar cells has been widespread and is growing. Only its chief rival, silicon, is more popular as a high-efficiency material. To continue gallium arsenide's growth, this research was conducted for the purpose of finding improved models for single-crystal GaAs solar cells. The research objectives were: (1) to characterize experimental GaAs cells, (2) to develop predictive device models for AlGaAs/GaAs, and (3) to project the potential of GaAs-based cells. Considering the number of laboratories fabricating GaAs solar cells, there has been a surprisingly limited number of experimental studies that have sought the understanding of GaAs device physics. To extend our knowledge in this area, a study of laboratory-grown cells was conducted. The goal was to uncover the mechanism that limit the performance of today's best GaAs solar cells. The information derived from this study has been used to develop improved models that successfully predict GaAs solar-cell performance. A two-dimensional numerical simulation program, capable of modeling GaAs/AlGaAs heterostructures, was developed. The simulation program is the culmination of earlier research efforts to GaAs/AlGaAs device modeling. It is not possible, using the numerical simulation program, to accurately assess the potential of GaAs solar cells. The numerical model projects conversion efficiencies of over 30% under concentrated sunlight, supporting earlier forecasts that GaAs could play an integral part of future solar-cell technology.

DeMoulin, P.D.

1988-01-01

295

Survival of rabbit platelets labeled with gallium 67  

SciTech Connect

The viability of rabbit platelets labeled with radioactive gallium was determined to analyze the feasibility of using platelets labeled with gallium 67 as an imaging reagent for positron emission tomography. Platelets were labeled with a complex of the longer lived gallium 67 and mercaptopyridine-N-oxide (MPO) or with sodium chromate Cr 51. Their survival after transfusion was measured. Labelling efficiency of /sup 67/Ga-MPO was 6.5% to 45.8% (26.8% +/- 2.8%) when platelets were suspended in saline solution, but was much lower (1.6% +/- 0.8%) in plasma. Platelets labeled with either radioisotope in a saline medium survived as well as platelets labeled with 51Cr in plasma. Recovery values 1 hour after transfusion and mean platelet survivals were 68.6% +/- 4.9% and 3.4 +/- 0.2 days for /sup 67/Ga in saline solution, 76.5% +/- 6.8% and 3.8 +/- 0.5 days for /sup 51/Cr in saline solution, and 73.7% +/- 7.4% and 3.6 +/- 0.5 days for /sup 51/Cr in plasma. Labeled platelet concentrates always contained extra radioactivity not firmly bound to viable platelets. A postlabeling wash in saline solution did not reduce this contamination and resulted in reduction of the number of viable platelets. The results showed that rabbit platelets labeled with /sup 67/Ga-MPO survived in the circulation as well as those labeled by a standard protocol with sodium chromate Cr 51.

Mazoyer, E.; Carpenter, D.; Ebbe, S.; Yano, Y.; Dalal, K.; Singh, M.; Mazoyer, B.

1988-02-01

296

Properties of gallium phosphide films prepared by rf magnetron sputtering  

NASA Astrophysics Data System (ADS)

As a coating material with excellent durability in 8 - 12 micrometers waveband, GaP films can be used as anti-reflective and protective layers on the windows and domes of ZnS, ZnSe and Ge. In this paper GaP films have been deposited by radio frequency magnetron sputtering of single crystalline gallium phosphide. The deposition rate, composition, structure, hardness and optical properties of GaP films have been investigated, and it's application used as anti-reflective and protective films on ZnS substrate has also been studied.

Song, Jianquan; Liu, Zhengtang; Guo, Dagang; Yu, Zhongqi; Geng, Dongsheng; Zheng, Xiulin

2000-11-01

297

Optical properties of gallium phosphide (GaP) nanowires  

NASA Astrophysics Data System (ADS)

The linear and non-linear optical properties of different geometrical structures of gallium phosphide (GaP) nanowires have been studied by employing ab initio method. We have calculated the optical response of four different GaP nanowires, viz., two atom linear wire, two atom zigzag wire, four atom square wire and six atom hexagonal wire. We have investigated imaginary part of the zz component of the linear dielectric tensor and second order susceptibility for different structures along with bulk material. We revealed that strongest absorption occurs for four atom square nanowire configuration.

Singh, Satyendra; Srivastava, Pankaj

2013-04-01

298

Gallium Phosphide as a material for visible and infrared optics  

NASA Astrophysics Data System (ADS)

Gallium phosphide is interesting material for optical system working in both visible and MWIR or LWIR spectral ranges. Number of a material available for these applications is limited. They are typically salts, fluorides or sulphides and usually exhibit unfavorable properties like brittleness; softness; solubility in water and small chemical resistance. Although GaP has do not offer best optical parameters excels over most other material in mechanical and chemical resistance. The article describes its most important characteristics and outlines some applications where GaP should prove useful.

Václavík, J.; Vápenka, D.

2013-04-01

299

Degradation phenomena in gallium aluminium arsenide stripe geometry lasers  

NASA Astrophysics Data System (ADS)

Gallium aluminium arsenide CW stripe lasers are capable of operating for at least several years at room temperature. However, both bulk and surface degradation still occur. Point defects incorporated during processing and strain associated with oxide isolation layers can influence bulk degradation; facet protection modifies surface effects. At higher temperatures, bond deterioration and localized bulk effects are more important than at room temperature. In order to justify the validity of temperature overstress testing, degradation mechanisms must be shown to be the same under operational and overstress conditions. Statistical analysis of data suggests that higher temperature degradation data cannot automatically be extrapolated via an Arrhenius-type relationship to yield meaningful operational lives.

Newman, D. H.; Ritchie, S.

1980-03-01

300

Gallium interstitial in irradiated germanium: Deep level transient spectroscopy  

SciTech Connect

Two electronic levels at 0.34 eV above the valence band and 0.32 eV below the conduction band, in gallium doped, p-type Ge irradiated with 2 MeV electrons have been studied by deep level transient spectroscopy (DLTS) with both majority- and minority-carrier injections, and Laplace DLTS spectroscopy. It is concluded that these levels, having donor and acceptor characters, respectively, are correlated with interstitial Ga atoms, formed by the Watkins-replacement mechanism via self-interstitials.

Kolkovsky, Vl.; Petersen, M. Christian; Larsen, A. Nylandsted [Department of Physics and Astronomy and Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, DK-8000 Aarhus C (Denmark); Mesli, A. [Institut d'Electronique du Solide et des Systemes, CNRS/ULP, Strasbourg (France); Gheluwe, J. van; Clauws, P. [Department of Solid State Sciences, Ghent University, B-9000 Ghent (Belgium)

2008-12-15

301

OMVPE of gallium arsenide using an adduct compound  

NASA Astrophysics Data System (ADS)

Organometallic vapor phase epitaxial (OMVPE) growth of gallium arsenide was conducted by making use of the reaction between an adduct compound: trimethygallium triethlphosphine and arsine. Characteristics of this growth process and the grown crystals were described in terms of growth rate, surface morphology, carrier concentration, electron mobility and photoluminescence spectra at 4 K. The highest mobilities obtained so far were 700 sq cm/(Vs) at 300 K and 47000 sq cm/(Vs) at 77 K. The lowest carrier concentration was 5 x 10 to the 14th per cu cm.

Minagawa, S.; Nakamura, H.; Sano, H.

1984-07-01

302

Geometrically induced melting variation in gallium clusters from first principles  

NASA Astrophysics Data System (ADS)

First-principles Born-Oppenheimer molecular dynamics simulations of gallium clusters reproduce experimental specific heats to a high degree of accuracy, with no experimental input or fitting. Remaining systematic shifts of the melting temperature highlight important limitations of density-functional approximations. An analysis of the structural changes observed as a function of finite temperature provides evidence for the assignment of a melting temperature to a specific peak in the specific heat. The structural basis for features in the specific heat curves, in particular, the existence of multiple peaks, is demonstrated.

Steenbergen, K. G.; Gaston, N.

2013-10-01

303

Technetium-99m DTPA aerosol and gallium scanning in acquired immune deficiency syndrome  

SciTech Connect

In 11 non-smoking AIDS patients suspected of pneumocystis carinii pneumonia (PCP), the results of Tc-99m DTPA aerosol clearances, gallium scans, and arterial blood gases were compared with those of bronchoalveolar lavage (BAL). Nine patients had PCP. All had increased clearances five times higher than the normal (5.6 +/- 2.3% X min-1 vs 1.1 +/- 0.34% X min-1, N = 10, P less than 0.001), suggesting an increased alveolar permeability. Gallium scans were abnormal in six patients but normal or slightly abnormal in the three others. Four of these nine patients had normal chest x-rays. In two of these the gallium scan was abnormal, but in the two others, only the increased Tc-99m DTPA clearances showed evidence of lung disease. Two patients had normal BAL, with normal clearances and gallium scans. Four out of the nine patients with PCP were studied after treatment. Three recovered and had normal clearance and gallium scans. One still had PCP with increased clearance but normal gallium scan. Gallium scanning and Tc-99m DTPA clearance are useful for detecting lung disease in AIDS patients with suspected PCP and for prompting BAL when chest x-rays and PaO/sub 2/ levels are normal. Due to its high sensitivity, a normal Tc-99m DTPA clearance could avoid BAL.

Picard, C.; Meignan, M.; Rosso, J.; Cinotti, L.; Mayaud, C.; Revuz, J.

1987-07-01

304

Tomographic gallium-67 citrate scanning: useful new surveillance for metastatic melanoma  

SciTech Connect

Conventional gallium scans are not useful to evaluate patients with metastatic melanoma. We evaluated a new method of tomographic gallium imaging. One hundred fourteen tomographic scans were obtained in a prospective surveillance study of 67 patients over a 3-year period. Scans were evaluated and compared to findings of independent clinical evaluations. Sensitivity of gallium identification of tumor involving peripheral lymph nodes and soft tissues, abdomen, mediastinum, and osseous sites was 68% to 100%; overall sensitivity of this technique is 82% with specificity of 99% in 570 organ system assessments. Analysis of discordant findings when a site was clinically occult but gallium-positive showed gallium uptake to be true-positive in six of seven lymphatic sites, three of three lung and mediastinal sites, six of six abdominal sites, but in no brain or bone sites. Gallium lesions identified by computed tomographic scans proved to be false-positive at one lymphatic and one bone site, and false-negative at four otherwise clinically evident lymph node and soft tissue sites, seven pulmonary sites, and four brain sites. Gallium tomographic scanning provides a composite assessment of melanoma and may eliminate the need for other studies.

Kirkwood, J.M.; Myers, J.E.; Vlock, D.R.; Neumann, R.; Ariyan, S.; Gottschalk, A.; Hoffer, P.

1982-11-01

305

Tomographic gallium-67 citrate scanning. Useful new surveillance for metastatic melanoma  

SciTech Connect

Conventional gallium scans are not useful to evaluate patients with metastatic melanoma. We evaluated a new method of tomographic gallium imaging. One hundred fourteen tomographic scans were obtained in a prospective surveillance study of 67 patients over a 3-year period. Scans were evaluated and compared to findings of independent clinical evaluations. Sensitivity of gallium identification of tumor involving peripheral lymph nodes and soft tissues, abdomen, mediastinum, and osseous sites was 68% to 100%; overall sensitivity of this technique is 82% with specificity of 99% in 570 organ system assessments. Analysis of discordant findings when a site was clinically occult but gallium-positive showed gallium uptake to be true-positive in six of seven lymphatic sites, three of three lung and mediastinal sites, six of six abdominal sites, but in no brain or bone sites. Gallium lesions identified by computed tomographic scans proved to be false-positive at one lymphatic and one bone site, and false-negative at four otherwise clinically evident lymph node and soft tissue sites, seven pulmonary sites, and four brain sites. Gallium tomographic scanning provides a composite assessment of melanoma and may eliminate the need for other studies.

Kirkwood, J.M.; Myers, J.E.; Vlock, D.R.; Neumann, R.; Ariyan, S.; Gottschalk, A.; Hoffer, P.

1983-07-01

306

Incorporation of nitrogen in GaAsN and InGaAsN alloys investigated by FTIR and NRA  

Microsoft Academic Search

InGaAsN layers grown by molecular beam epitaxy were investigated using Fourier transform infrared absorption spectroscopy. The nitrogen-related local mode at 471cm?1 is used as a quantitative tool to assess the substitutional nitrogen fraction. Evidence is presented that nitrogen in the quaternary alloy is bonded only to gallium atoms as in GaAsN. No change in the local environment of nitrogen is

H. Ch. Alt; A. Yu. Egorov; H. Riechert; J. D. Meyer; B. Wiedemann

2001-01-01

307

BRAZING ALLOYS  

DOEpatents

A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

1962-02-20

308

COATED ALLOYS  

DOEpatents

A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

Harman, C.G.; O' Bannon, L.S.

1958-07-15

309

Electrodeposition of crystalline GaAs on liquid gallium electrodes in aqueous electrolytes.  

PubMed

Crystalline GaAs (c-GaAs) has been prepared directly through electroreduction of As(2)O(3) dissolved in an alkaline aqueous solution at a liquid gallium (Ga(l)) electrode at modest temperatures (T ? 80 °C). Ga(l) pool electrodes yielded consistent electrochemical behavior, affording repetitive measurements that illustrated the interdependences of applied potential, concentration of dissolved As(2)O(3), and electrodeposition temperature on the quality of the resultant c-GaAs(s). Raman spectra indicated the composition of the resultant film was strongly dependent on both the electrodeposition temperature and dissolved concentration of As(2)O(3) but not to the applied bias. For electrodepositions performed either at room temperature or with high (?0.01 M) concentrations of dissolved As(2)O(3), Raman spectra of the electrodeposited films were consistent with amorphous As(s). X-ray diffractograms of As(s) films collected after thermal annealing indicated metallurgical alloying occurred only at temperatures in excess of 200 °C. Optical images and Raman spectra separately showed the composition of the as-electrodeposited film in dilute (?0.001 M) solutions of dissolved As(2)O(3)(aq) was pure c-GaAs(s) at much lower temperatures than 200 °C. Diffractograms and transmission electron microscopy performed on as-prepared films confirmed the identity of c-GaAs(s). The collective results thus provide the first clear demonstration of an electrochemical liquid-liquid-solid (ec-LLS) process involving a liquid metal that serves simultaneously as an electrode, a solvent/medium for crystal growth, and a coreactant for the synthesis of a polycrystalline semiconductor. The presented data serve as impetus for the further development of the ec-LLS process as a controllable, simple, and direct route for technologically important optoelectronic materials such as c-GaAs(s). PMID:23265429

Fahrenkrug, Eli; Gu, Junsi; Maldonado, Stephen

2012-12-24

310

[Determination of traces of gallium in air by oscillographic polarography].  

PubMed

Gallium and its compounds in air collected by millipore filter membrane are leached by 10% HNO3 at room temperature. After being adjusted with ammonia solution to pH8-9, the leachate is filtered and the filtrate is evaporated to dryness on a water bath. The residue is dissolved with 2 ml of 10% HNO3 and then into the solution are added 0.5 ml of 5% hydroxylamine hydrochloride solution, 0.20 ml of 5% sulfosalicyclic acid solution, 0.5 ml of NaF solution (1mg F/ml) and 1 drop of methyl red solution. Let it stand for 5 min after the color of the solution turns orange by addition of 1:1 NH4OH solution. Add 0.20ml of 0.20% cupferron solution, 0.20ml of 0.5% diphenyl-guanidine solution (prepared in 95% ethanol) and 0.5ml of acetic acid-ammonium acetate buffer (pH 7.0). Then add water to make the final volume of the test solution to be 10ml and measure the height of the second derivative polarographic wave at -1.08V (vs.SCE). The sensitivity of the method is 0.005-0.10 microgram/ml, the coefficient of variation 6.8%, recovery 97.8%. Within 0.005-0.10 microgram/ml, the wave height is linear with the concentration of gallium. PMID:2365333

Sun, C; Yang, Z; Cheng, D; Yi, Z; Shen, T; Liu, Z; Bai, Y

1990-03-01

311

Crystallographic alignment of high-density gallium nitride nanowire arrays.  

PubMed

Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration. PMID:15273744

Kuykendall, Tevye; Pauzauskie, Peter J; Zhang, Yanfeng; Goldberger, Joshua; Sirbuly, Donald; Denlinger, Jonathan; Yang, Peidong

2004-07-25

312

Gadolinium Gallium Garnet at Multi-Megabar Pressures  

NASA Astrophysics Data System (ADS)

Gadolinium gallium oxide Gd3Ga5O12, which crystallizes in the garnet structure, has recently attracted strong interest due to shock-wave experiments revealing a highly incompressible high-pressure phase above 1 Mbar [1]. In addition, recent diamond-cell x-ray diffraction experiments provide evidence for a phase transition from garnet to double-perovskite structures around 1 Mbar [2]. We present the results of laser-driven shock experiments on gadolinium gallium garnet (GGG) at pressures of 3 to more than 20 Mbar, obtained at the Omega-LLE and Jupiter-LLNL facilities, and compare these with the results of ab-initio molecular dynamic simulations. Velocimetry (VISAR) and pyrometry (SOP) diagnostics, and an impedance match analysis with quartz standards, provide data on the equation of state, temperature and optical reflectivity at 532 nm. No obvious phase transition is detected in the explored pressure range, but the data indicate that GGG remains surprisingly stiff up to more than 20 Mbar. We observe metallic-like reflectivity in the ultra-high pressure (possibly liquid) regime. This study could be relevant for planetary interior modeling, as many Earth and super-Earth minerals adopt the garnet and perovskite structures, and may exhibit transition to metallic and highly incompressible behavior.

Millot, M.; Ali, S. J.; Militzer, B.; Barrios, M. A.; Boehly, T.; Eggert, J. H.; Collins, G.; Jeanloz, R.

2011-12-01

313

Gallium nitride microcavities formed by photoenhanced wet oxidation  

SciTech Connect

We report the formation of gallium nitride (GaN) microcavities by manipulating a photoenhanced oxidation rate difference between the polar and nonpolar crystallographic planes of GaN. When immersed in a buffered acetic (CH{sub 3}COOH) electrolyte of pH{approx}6.2 at room temperature, it is shown that the photo-oxidation can proceed at a rate that is one order of magnitude slower on the nonpolar plane of {l_brace}1100{r_brace}{sub GaN} than on the polar plane of {l_brace}0001{r_brace}{sub GaN} due to the reduced surface field action. Gallium nitride microcavities bounded by optically smooth {l_brace}1100{r_brace} and {l_brace}1103{r_brace} facets can thus be preferentially formed on the c-plane sapphire substrate after dissolving the oxide layer. The optical properties of these GaN hexagonal cavities reveal characteristic peaks of whispering gallery modes in resonance with the GaN band edge emission spectrum. A typical cavity Q factor of 10{sup 3} is observed in these GaN microcavities due to a reduced optical scattering loss in the wet chemical reaction process.

Peng, L.-H.; Lu, C.-Y.; Wu, W.-H.; Wang, S.-L. [Department of Electrical Engineering and Institute of Electro-Optical Engineering, National Taiwan University, Taipei, Taiwan (China)

2005-10-17

314

Anion ordering in spinel-type gallium oxonitride  

NASA Astrophysics Data System (ADS)

The specific locations of the anions—nitrogen and oxygen—in the crystallographic sites are not known in the spinel-type gallium oxonitride. We report here on an indirect method for determining the specific location of the light elements N and O in a defect spinel-structured gallium oxonitride, Ga2.79O3.05N0.76. The locations of elements that are adjacent in the periodic table (?Z=±1) are indistinguishable with conventional x-ray diffraction techniques. However, by examining the local electronic structure we show that the anions are spatially ordered such that R3¯m (no. 166) is the most appropriate defect-free space group. Finally, we determined the electronic band gap of Ga2.79O3.05N0.76 experimentally to be 2.95 ± 0.30, agreeing with our calculated value of 2.79 eV (direct) for Ga3O3N using a local density approximation functional including a semilocal potential modified from that of Becke and Johnson (the MBJLDA functional).

Boyko, Teak D.; Zvoriste, Carmen E.; Kinski, Isabel; Riedel, Ralf; Hering, Stefanie; Huppertz, Hubert; Moewes, Alexander

2011-08-01

315

Biochemical mechanism of gallium on prevention of fatal cage-layer osteoporosis.  

PubMed

The possible biochemical mechanism of gallium was studied in this paper. One-day-old hens were fed to up to 68 weeks on a control diet and diets containing gallium. Serum calcium and phosphorus, serum alkaline phosphatase, tartrate resistant acid phosphatase (TRAP), serum osteocalcin, homocysteine, C-terminal crosslinked telopeptides of collagen type I, and bone mineral content were measured, respectively. The beneficial effects of gallium supplementation on improvement of cage layer osteoporosis were attributable mainly to decrease TRAP activity, C-terminal crosslinked telopeptides of collagen type I level, plasma calcium and phosphate concentrations, and increase the mineral content in the bones and osteocalcin level in plasma. PMID:19639269

Li, Chunxiang; Jiang, Zheng; Liu, Xinghan

2009-07-29

316

Photochemistry of trimethylgallium with application to atomic gallium reaction kinetics. [Trimethylgallium  

SciTech Connect

The photodissociation of gas-phase trimethylgallium at 193 nm has been investigated using the laser photolysis/laser induced fluorescence technique. Gallium atoms are produced by multiple-photon processes during the time of the excimer laser pulse and continue to be produced at long times after the photolysis pulse. The observed dependences on photolysis laser fluence, trimethylgallium pressure, and buffer gas pressure are consistent with a mechanism in which highly excited gallium methyl radicals undergo unimolecular decomposition to produce gallium atoms. Since this process can happen on time scales long compared to the photolysis laser pulse, these results may have important implications for studies of laser deposition of thin metal films.

Baughcum, S.L.; Oldenborg, R.C.

1985-01-01

317

Polycrystalline Thin-Film Research: Copper Indium Gallium Diselenide (Fact Sheet)  

SciTech Connect

Capabilities fact sheet for the National Center for Photovoltaics: Polycrystalline Thin-Film Research: Copper Indium Gallium Diselenide that includes scope, core competencies and capabilities, and contact/web information.

Not Available

2011-06-01

318

Empyema of the gallbladder detected by gallium scan and abdominal ultrasonography  

SciTech Connect

A case history of patient with a abnormal gallium uptake and sonogram in the region of the gallbladder is described. The abnormality was interpreted as empyema of the gallbladder and later proven surgically. A liver-spleen scan was normal except for slight prominence of the hilar structures. Gallium citrate Ga-67 scans done at 24 and 48 hours showed a persistent area of increased tracer localization around the gallbladder with a central clear zone in the latter scan. Ultrasonography revealed poor definition and slight thickening of the gallbladder wall. Because of the lack of specificity of gallium scans, the combination of ultrasonic imaging and gallium uptake scans appears much superior in diagnostic efficiency than either of the two alone. The sequence of performing these two examinations does not seem to be critical though it was prefered that the scintigraphy precede the sonography.

Garcia, O.M.; Kovac, A.; Plauche, W.E.

1981-08-01

319

Homogeneous dispersion of gallium nitride nanoparticles in a boron nitride matrix by nitridation with urea.  

PubMed

A Gallium Nitride (GaN) dispersed boron nitride (BN) nanocomposite powder was synthesized by heating a mixture of gallium nitrate, boric acid, and urea in a hydrogen atmosphere. Before heat treatment, crystalline phases of urea, boric acid, and gallium nitrate were recognized, but an amorphous material was produced by heat treatment at 400 degrees C, and then was transformed into GaN and turbostratic BN (t-BN) by further heat treatment at 800 degrees C. TEM obsevations of this composite powder revealed that single nanosized GaN particles were homogeneously dispersed in a BN matrix. Homogeneous dispersion of GaN nanoparticles was thought to be attained by simultaneously nitriding gallium nitrate and boric acid to GaN and BN with urea. PMID:21128417

Kusunose, Takafumi; Sekino, Tohru; Ando, Yoichi

2010-07-01

320

Gallium Content in PuO{sub 2} Using Laser Induced Breakdown Spectroscopy (LIBS)  

SciTech Connect

Laser Induced Breakdown Spectroscopy (LIBS) has been applied to the semi-quantitative analysis of gallium in plutonium oxide at the Los Alamos Plutonium Facility. The oxide samples were generated by the Thermally Induced Gallium Removal (TIGR) process, a pretreatment step prior to MOX fuel processing. The TIGR process uses PuO{sub 2} containing 1 wt% gallium (nominal) as feed material. Following the TIGR process, gallium content was analyzed by LIBS and also by conventional wet chemical analysis (ICP-MS). Although the data range was insufficient to obtain an adequate calibration, general agreement between the two techniques was good. LIBS was found to have a useful analytical range of 34-400 ppm for Ga in PuO{sub 2}.

Smith, C.A.; Martinez, M.A.; Veirs, D.K.

1999-08-29

321

Two-Photon Optical-Beam-Induced Current Microscopy of Indium Gallium Nitride Light Emitting Diodes.  

National Technical Information Service (NTIS)

In this study, epilayers of packaged indium gallium nitride light emitting diodes (LED's) are characterized by optical beam induced current (OBIC) and photoluminescence laser scanning microscopy through two-photon excitation. OBIC reveals spatial and elec...

F. Kao M. Huang M. Lee S. L. Huang Y. Wang

2000-01-01

322

Gallium-67 detection of intramammary injection sites secondary to intravenous drug abuse  

SciTech Connect

A case of gallium localization within the breast occurred secondary to intravenous drug abuse. In the appropriate clinical setting, prior self-administered injections should be considered as a cause of Ga-67 accumulation at unusual sites.

Swayne, L.C. (Morristown Memorial Hospital, NJ (USA))

1989-09-01

323

Fabrication and Characterization of Sub100 mum Diameter Gallium Phosphide Solid Immersion Lens Arrays  

Microsoft Academic Search

Fabrication and testing of a sub-100 mum gallium phosphide solid immersion lens is described with suitable sphericity (<160 nm deviation) to a marginal ray angle of 42° for NA up to 2.2 inside the material.

Matthew Lang; Tom D. Milster; Takahisa Minamitani; Gregg Borek; David Brown

2005-01-01

324

Epitaxial cubic gadolinium oxide as a dielectric for gallium arsenide passivation  

PubMed

Epitaxial growth of single-crystal gadolinium oxide dielectric thin films on gallium arsenide is reported. The gadolinium oxide film has a cubic structure isomorphic to manganese oxide and is (110)-oriented in single domain on the (100) gallium arsenide surface. The gadolinium oxide film has a dielectric constant of approximately 10, with low leakage current densities of about 10(-9) to 10(-10) amperes per square centimeter at zero bias. Typical breakdown field is 4 megavolts per centimeter for an oxide film 185 angstroms thick and 10 megavolts per centimeter for an oxide 45 angstroms thick. Both accumulation and inversion layers were observed in the gadolinium oxide-gallium arsenide metal oxide semiconductor diodes, using capacitance-voltage measurements. The ability to grow thin single-crystal oxide films on gallium arsenide with a low interfacial density of states has great potential impact on the electronic industry of compound semiconductors. PMID:10082459

Hong; Kwo; Kortan; Mannaerts; Sergent

1999-03-19

325

Gallium nitride (GaN) HEMT's: progress and potential for commercial applications  

Microsoft Academic Search

This paper focuses on the development of 100 mm gallium nitride HEMT technology at RF Micro Devices and the utilization of GaN transistors for commercial applications such as power amplifiers, power switches and low-noise power oscillators.

J. Shealy; J. Smart; M. Poulton; R. Sadler; D. Grider; S. Gibb; B. Hosse; B. Sousa; D. Halchin; V. Steel; P. Garber; P. Wilkerson; B. Zaroff; J. Dick; T. Mercier; J. Bonaker; C. Greer; M. Isenhour

2002-01-01

326

P-i-n structures based on high-ohmic gettered gallium arsenide for ? particle detectors  

NASA Astrophysics Data System (ADS)

It is shown that p-i-n detectors of ? particles can be created using high-ohmic ( n ˜ 1012 cm-3) gallium arsenide obtained through lanthanide gettering of a low-ohmic ( n ˜ 1015 cm-3) initial material wafers.

Gorelenok, A. T.; Tomasov, A. A.; Shmidt, N. M.; Il'Ichev, É. A.; Lantratov, V. M.; Zadiranov, Yu. M.; Brunkov, P. N.; Titkova, O. V.; Kalyuzhny?, N. A.; Mintarov, S. A.; Mdivani, V. N.; Katsoev, V. V.; Katsoev, L. V.; Shmelev, S. S.

2006-11-01

327

Deep Level Defects in Electron-Irradiated Aluminum Gallium Nitride Grown by Molecular Beam Epitaxy.  

National Technical Information Service (NTIS)

Aluminum gallium nitride (AlGaN)-based devices are attractive candidates for integration into future Air Force communication and sensor platforms, including those that must operate in harsh radiation environments. In this study, the electrical and optical...

M. R. Hogsed

2005-01-01

328

Magnetic refrigeration cycle analysis using selected thermodynamic property characterizations for gadolinium gallium garnet.  

National Technical Information Service (NTIS)

Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorpor...

R. W. Murphy

1992-01-01

329

Determination of gallium concentration in blood-free tissues using a radiolabeled blood marker  

SciTech Connect

Radioiodinated serum albumin has been used as a blood marker to define and quantitate physiological volumes for 12 organs and tissue types. The concentration of gallium-67 in blood-free tissues of rats was also determined at various times after intravenous administration. Tissues were divided into two kinetically distinguishable types based on reported nonuniform distribution of the blood marker and the gallium distribution observed in the present study. Gallium distribution into the liver and spleen was observed to be slow, with a discernable accumulation phase followed by monoexponential elimination. In contrast, gallium accumulation into the stomach, small and large intestines, heart, lung, skin/adipose tissue, and muscle was rapid and elimination was monophasic.

Triplett, J.W.; Hayden, T.L.; McWhorter, L.K.; Gautam, S.R.; Kim, E.E.; Bourne, D.W.

1985-09-01

330

Haemophilus parainfluenzae bacteremia associated with a pacemaker wire localized by gallium scan  

SciTech Connect

A young woman with a history of sick sinus syndrome and placement of a permanent pacemaker 6 months before admission had fever and Haemophilus parainfluenzae bacteremia. A gallium scan localized the infection to the site of the pacemaker wire. Echocardiograms were negative for any vegetations. The patient responded to cefotaxime and trimethoprim-sulfamethoxazole therapy. We believe that this is the first case of H. parainfluenzae bacteremia associated with a pacemaker wire and localized by gallium scan.

Rosenbaum, G.S.; Calubiran, O.; Cunha, B.A. (Winthrop-Univ. Hospital, Mineola, NY (USA))

1990-05-01

331

Gallium nitrate inhibits calcium resorption from bone and is effective treatment for cancer-related hypercalcemia  

Microsoft Academic Search

Approximately two-thirds of patients who receive the anticancer drug gallium nitrate develop mild hypocalcemia. To evaluate the mechanism of drug-induced hypocalcemia, we tested the effects of gallium nitrate upon in vitro release of ⁴⁵Ca++ from explanted fetal rat bones. The drug significantly inhibited ⁴⁵Ca++ release in response to stimulation with both parathyroid hormone and a lymphokine preparation with osteoclast activating

R. P. Jr. Warrell; R. S. Bockman; C. J. Coonley; M. Isaacs; H. Staszewski

1984-01-01

332

Relative efficacy of chelating agents as antidotes for acute gallium nitrate intoxication  

Microsoft Academic Search

Twelve chelating agents were administered to mice by IP injection to compare their relative effectiveness in preventing death after a single IP injection of gallium nitrate. Na2Ca-ethylenediaminetetraacetate (EDTA), Na3Ca-diethylenetriaminepentaacetate (DTPA), dimercaptosuccinic acid (DMSA), 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron), sodium diethyldithiocarbamate (DDC), L-cysteine and sodium salicylate were not effective for acute gallium nitrate intoxication. The therapeutic indices of the effective chelators were: 25.4

José L. Domingo; Juan M. Llobet; Jacinto Corbella

1987-01-01

333

Recent Advances in Gallium Phosphide Junction Devices for High-Temperature Electronic Applications  

Microsoft Academic Search

Recent advances in gallium phosphide technology are reviewed as they relate to high-temperature (T > 300°C) device applications. The electronic properties and materials aspects of GaP are summarized and compared to silicon and gallium arsenide. Minority-carrier unction devices are discussed as one area where this technology could have wide application. In this light, the high-temperature operation of two junction devices,

Thomas E. Zipperian; Roger J. Chaffin; L. Ralph Dawson

1982-01-01

334

Are oral cathartics of value in optimizing the gallium scan. Concise communication  

SciTech Connect

The normal intestinal secretion of 9-15% of an administered dose of gallium-67 may prevent early detection of intra-abdominal disease. We randomized 50 patients to receive either no bowel preparation or 30 cc of milk of magnesia plus 5 cc of cascara. No significant difference was found between the two groups in frequency with which gallium interfered with readings or time to complete the study.

Silberstein, E.B.; Fernandez-Ulloa, M.; Hall, J.

1981-05-01

335

First Results of the Testing of the Liquid Gallium Jet Limiter Concept for ISTTOK  

SciTech Connect

The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages to the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaustion from fusion devices. Presently the most promising materials are Lithium and Gallium. ISTTOK, a small size tokamak, will be used to test the behavior of a liquid Gallium jet in the vacuum chamber and its influence on the plasma. This paper presents a description of the conceived setup as well as experimental results. The liquid Gallium jet is generated by hydrostatic pressure and injected in a radial position close to a moveable stainless steel limiter. Both the jet and the limiter positions are variable allowing for a controlled exposure of the liquid Gallium to the edge plasma. The main components of the Gallium loop are a MHD pump, the liquid metal injector and a filtering system. The MHD pump is of the induction type, based on rotating permanent magnets. The injector is build from a stainless steel pipe ended by a shaping nozzle. A setup has been developed to introduce oxide-free Gallium inside the loop's main supply tank. Raw liquid metal is placed inside a chamber heated and degassed under high vacuum while clean Gallium is extracted from the main body of the liquefied metal. Prior to installation on the tokamak, the experimental rig has been implemented using a Pyrex tube as test chamber to investigate the stability of the Gallium jet and its break-up length for several nozzle sizes. Results are presented in this paper. This rig was also useful to assess the behavior of the overall implemented apparatus.

Gomes, R. B.; Fernandes, H.; Silva, C.; Borba, D.; Carvalho, B.; Varandas, C. [Associacao EURATOM/IST, Centro de FuSao Nuclear, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Lielausis, O.; Klyukin, A.; Platacis, E.; Mikelsons, A.; Platnieks, I. [Association EURATOM/University of Latvia, Institute of Physics, 32 Miera Str., Salaspils, LV-2169 (Latvia)

2006-12-04

336

Characterization of gallium nitride-based high electron mobility transistor devices  

Microsoft Academic Search

High electron mobility transistors (HEMTs) consisting of aluminum gallium nitride (AlGaN) - gallium nitride (GaN) heterostructures have been characterized by advanced electron microscopy methods including off-axis electron holography, nanoscale chemical analysis, and in situ electrical biasing. The research was divided into three parts: (1) Site-specific sample preparation using focused-ion-beam (FIB) and other complementary techniques; (2) Off-axis electron holography to image

David A. Cullen

2010-01-01

337

Growth and Characteristics Analysis of the Thermal Oxide Grown on Gallium Nitride  

Microsoft Academic Search

The thermal oxidation process at 900degC in dry oxygen 02 on gallium nitride (GaN) and the physical characteristics of the oxide thin films are investigated by spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS). XPS spectra of Ga3d and O1s core levels indicates that the thermal oxide is gallium oxide (Ga2O3), and the existence of much O loss on the

Jiangfeng Du; Jinxia Zhao; Qian Luo; Zhiwei Yu; Jianxin Xia; Mohua Yang

2009-01-01

338

Controlled delivery of antimicrobial gallium ions from phosphate-based glasses.  

PubMed

Gallium-doped phosphate-based glasses (PBGs) have been recently shown to have antibacterial activity. However, the delivery of gallium ions from these glasses can be improved by altering the calcium ion concentration to control the degradation rate of the glasses. In the present study, the effect of increasing calcium content in novel gallium (Ga2O3)-doped PBGs on the susceptibility of Pseudomonas aeruginosa is examined. The lack of new antibiotics in development makes gallium-doped PBG potentially a highly promising new therapeutic agent. The results show that an increase in calcium content (14, 15 and 16 mol.% CaO) cause a decrease in degradation rate (17.6, 13.5 and 7.3 microg mm(-2) h(-1)), gallium ion release and antimicrobial activity against planktonic P. aeruginosa. The most potent glass composition (containing 14 mol.% CaO) was then evaluated for its ability to prevent the growth of biofilms of P. aeruginosa. Gallium release was found to reduce biofilm growth of P. aeruginosa with a maximum effect (0.86 log(10) CFU reduction compared to Ga2O3-free glasses) after 48 h. Analysis of the biofilms by confocal microscopy confirmed the anti-biofilm effect of these glasses as it showed both viable and non-viable bacteria on the glass surface. Results of the solubility and ion release studies show that this glass system is suitable for controlled delivery of Ga3+. 71Ga NMR and Ga K-edge XANES measurements indicate that the gallium is octahedrally coordinated by oxygen atoms in all samples. The results presented here suggest that PBGs may be useful in controlled drug delivery applications, to deliver gallium ions in order to prevent infections due to P. aeruginosa biofilms. PMID:18974026

Valappil, S P; Ready, D; Abou Neel, E A; Pickup, D M; O'Dell, L A; Chrzanowski, W; Pratten, J; Newport, R J; Smith, M E; Wilson, M; Knowles, J C

2008-10-10

339

Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd3Ga5O12 substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 ?m showing good crystalline quality and epitaxial growth.

Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Jörg K. N.; Stritzker, Bernd

2006-04-01

340

Sequential technetium-99m HMDP-gallium-67 citrate imaging for the evaluation of infection in the painful prosthesis  

SciTech Connect

In order to evaluate the clinical utility of sequential technetium-99m HMDP-gallium-67 scanning in patients with painful orthopedic prosthesis, a retrospective review was made of 154 sequential scans performed in 130 patients. Criteria for a positive study included spatially incongruent gallium-technetium uptake or gallium uptake that was congruent but more intense than technetium. Images were interpreted as negative if gallium was congruent and less intense than technetium. Sixty-six patients underwent surgery (31 infected, 35 aseptic), and 64 were evaluated clinically (3 infected, 61 aseptic). The combined results of the surgical and nonsurgical patients yielded a sensitivity of 66%, a specificity of 81%, and an accuracy of 77%. In this series, the technetium-gallium scan combination has proven to be helpful but more recent techniques such as indium-111-labeled leukocytes may prove to be superior to sequential technetium-gallium imaging.

Merkel, K.D.; Brown, M.L.; Fitzgerald, R.H. Jr.

1986-09-01

341

Concerning the energy levels of silver in Ge-Si alloys  

SciTech Connect

The emission from impurity states of silver (an element of the IB subgroup) in a Ge-Si alloy, containing 18 at % Si, has been studied. The donor level of silver has been found in crystals doubly doped with gallium and silver, while its first acceptor level has been revealed in crystals doped with only silver. Single crystals were grown by pulling from a melt using a feeding rod. Doping with gallium was performed by introducing this element into the feeding rod, and silver was introduced into the crystals via diffusion. The positions of the donor and first acceptor Ag levels with respect to the top of the valence band were found by analyzing the temperature dependence of the Hall coefficient and the electroneutrality equation for the crystal: 0.06 and 0.29 eV, respectively.

Tahirov, V. I. [Baku State University (Azerbaijan); Agamaliev, Z. A. [National Academy of Sciences of Azerbaijan, Institute of Physics (Azerbaijan); Sadixova, S. R.; Guliev, A. F.; Gahramanov, N. F., E-mail: n_gakhramanov@mail.ru [Sumgait State University (Azerbaijan)

2012-03-15

342

Study of Bulk Modulus in Zincblende Nitrogen-doped Gallium Phosphide Alloys Using Density Functional Theory  

Microsoft Academic Search

The prospect of solar energy as a renewable resource is ever-increasing. Density functional theory (DFT) calculations can elicit reliable behavior predictions in energy conversion materials to achieve higher efficiencies. Chemical stability of the photo-catalysts in aqueous solution is of particular interest for its long term performances. The bulk modulus is a mechanical property that is a good indicator of material

Brandon M. Butler; John A. Turner; Muhammad N. Huda

2011-01-01

343

ZSM-5 catalysts having predominately framework gallium, methods of their preparation, and use thereof  

SciTech Connect

This patent describes a method of introducing gallium as a zeolitic element in the framework of ZSM-5, wherein the resulting gallium incorporated ZSM-5 is substantially free of non-framework gallium. It comprises preparing a ZSM-5 crystallization reaction mixture by forming a hydrogel containing a source of SiO{sub 2} and a source of Ga{sub 2}O{sub 3} wherein the SiO{sub 2} to the Ga{sub 2}O{sub 3} is present in a molar ratio of less than 100/1; adding to the reaction mixture an amount of Na{sub 2}SO{sub 4} such that the molar ratio of SiO{sub 2} to Na{sub 2}SO{sub 4} ranges from 20/1 to 0.1/1 and is effective to cause the gallium content of the resulting zeolite to be a zeolitic framework element; maintaining the reaction mixture under conditions effective to cause formation of the gallium incorporated ZSM-5 and recovering the gallium incorporated ZSM-5.

Chu, C.T.; Han, S.

1990-11-06

344

Strategies for gallium removal after focused ion beam patterning of ferroelectric oxide nanostructures.  

PubMed

As part of a study into the properties of ferroelectric single crystals at nanoscale dimensions, the effects that focused ion beam (FIB) processing can have, in terms of structural damage and ion implantation, on perovskite oxide materials has been examined, and a post-processing procedure developed to remove such effects. Single crystal material of the perovskite ferroelectric barium titanate (BaTiO(3)) has been patterned into thin film lamellae structures using a FIB microscope. Previous work had shown that FIB patterning induced gallium impregnation and associated creation of amorphous layers in a surface region of the single crystal material some 20 nm thick, but that both recrystallization and expulsion of gallium could be achieved through thermal annealing in air. Here we confirm this observation, but find that thermally induced gallium expulsion is associated with the formation of gallium-rich platelets on the surface of the annealed material. These platelets are thought to be gallium oxide. Etching using nitric and hydrochloric acids had no effect on the gallium-rich platelets. Effective platelet removal involved thermal annealing at 700 degrees C for 1 h in a vacuum followed by 1 h in oxygen, and then a post-annealing low-power plasma clean in an Ar/O atmosphere. Similar processing is likely to be necessary for the full recovery of post FIB-milled nanostructures in oxide ceramic systems in general. PMID:19636116

Schilling, A; Adams, T; Bowman, R M; Gregg, J M

2007-01-03

345

High-Temperature Decomposition of Brønsted Acid Sites in Gallium-Substituted Zeolites  

SciTech Connect

The dehydroxylation of Broensted acid sites (BAS) in Ga-substituted zeolites was investigated at temperatures up to 850 C using X-ray absorption spectroscopy (XAS), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry-temperature programmed desorption (MS-TPD). X-ray absorption near-edge spectroscopy (XANES) revealed that the majority of gallium has tetrahedral coordination even after complete dehydroxylation. The interatomic gallium-oxygen distance and gallium coordination number determined by extended X-ray absorption fine structure (EXAFS) are consistent with gallium in tetrahedral coordination at low T (< 550 C). Upon heating Ga-Beta and Ga-ZSM5 to 850 C, analysis of the EXAFS showed that 70 and 80% of the gallium was still in tetrahedral coordination. The remainder of the gallium was found to be in octahedral coordination. No trigonal Ga atoms were observed. FTIR measurements carried out at similar temperatures show that the intensity of the OH vibration due to BAS has been eliminated. MS-TPD revealed that hydrogen in addition to water evolved from the samples during dehydroxylation. This shows that dehydrogenation in addition to dehydration is a mechanism that contributes to BAS decomposition. Dehydrogenation was further confirmed by exposing the sample to hydrogen to regenerate some of the BAS as monitored by FTIR and MS-TPD.

K Al-majnouni; N Hould; W Lonergan; D Vlachos; R Lobo

2011-12-31

346

Strategies for gallium removal after focused ion beam patterning of ferroelectric oxide nanostructures  

NASA Astrophysics Data System (ADS)

As part of a study into the properties of ferroelectric single crystals at nanoscale dimensions, the effects that focused ion beam (FIB) processing can have, in terms of structural damage and ion implantation, on perovskite oxide materials has been examined, and a post-processing procedure developed to remove such effects. Single crystal material of the perovskite ferroelectric barium titanate (BaTiO3) has been patterned into thin film lamellae structures using a FIB microscope. Previous work had shown that FIB patterning induced gallium impregnation and associated creation of amorphous layers in a surface region of the single crystal material some 20 nm thick, but that both recrystallization and expulsion of gallium could be achieved through thermal annealing in air. Here we confirm this observation, but find that thermally induced gallium expulsion is associated with the formation of gallium-rich platelets on the surface of the annealed material. These platelets are thought to be gallium oxide. Etching using nitric and hydrochloric acids had no effect on the gallium-rich platelets. Effective platelet removal involved thermal annealing at 700 °C for 1 h in a vacuum followed by 1 h in oxygen, and then a post-annealing low-power plasma clean in an Ar/O atmosphere. Similar processing is likely to be necessary for the full recovery of post FIB-milled nanostructures in oxide ceramic systems in general.

Schilling, A.; Adams, T.; Bowman, R. M.; Gregg, J. M.

2007-01-01

347

Structural and Electrical Properties of Solution-Processed Gallium-Doped Indium Oxide Thin-Film Transistors  

Microsoft Academic Search

We fabricated solution-processed gallium-doped indium oxide (GIO) thin-film transistors (TFTs). The electrical property, crystallinity, and transmittance were investigated as a function of gallium content. Varying the gallium\\/indium ratio is found to have a significant effect on structural and electrical properties of thin films. The shrinkage of the lattice of a GIO film originates from substitution of Ga on In sites

Jee Ho Park; Won Jin Choi; Soo Sang Chae; Jin Young Oh; Se Jong Lee; Kie Moon Song; Hong Koo Baik

2011-01-01

348

Near-electrode processes in lanthanum-gallium tantalate crystals  

SciTech Connect

The near-electrode processes on the surfaces of the polar cuts of lanthanum-gallium tantalate crystals grown in different atmospheres were investigated. The temperature dependences of short-circuit currents in the temperature range 20-700{sup o}C were measured and phase analysis of the sample surfaces after the temperature tests were performed. It is shown that short-circuit currents arise on the surfaces of polar cuts with identical conducting coatings without preliminary polarization. These currents are caused by the generation of intrinsic emf as a result of the electrochemical reactions on opposite polar cut surfaces coming in contact with a conducting coating. It is established that the crystal growth atmosphere and the conducting coating material significantly affect the temperature dependences of short-circuit currents.

Buzanov, O. A. [OAO Fomos Materials (Russian Federation); Zabelina, E. V., E-mail: e.zabelina@gmail.com; Kozlova, N. S., E-mail: kozlova_nina@mail.ru; Sagalova, T. B. [Moscow State Institute of Steel and Alloys (Russian Federation)

2008-09-15

349

Some Curious Results with a Gallium Fixed-Point Cell  

NASA Astrophysics Data System (ADS)

In 2009, most of the gallium fixed-point cells in use in different INRIM laboratories were compared with Italy's national standard. The comparison has uncovered problems with one of the commercial devices, realizing a temperature about 0.7 mK too low which initially was even changing linearly with time. An additional series of measurements was undertaken to find out the reason for this behavior, but not being allowed to open the cell, only a suspicion on the possible cause has remained. A way is suggested that might give users an indication of such misbehavior of their cell. The results underline the importance for those NMIs with only a single cell, for any fixed point, to undertake regular comparisons with another cell as a check on its behavior.

Steur, P. P. M.; Dematteis, R.

2011-01-01

350

Synthesis and structural characterization of mixed aluminum-gallium-offretites.  

PubMed

A new synthesis procedure is reported for the preparation of mixed Al,Ga-offretites over the entire solid solution range 0 < or = Ga/(Ga + Al) < or = 1. The resulting materials are characterized by X-ray powder diffraction, adsorption microcalorimetry and multinuclear solid state NMR. The 29Si MAS-NMR data are consistent with statistical occupancy of the T1 and T2 sites by aluminum and gallium, and also show no positive evidence for preferential siting effects between both framework metals. Isotropic chemical shifts and nuclear electric quadrupolar coupling constants for 27Al and 71Ga have been obtained from a field-dependent analysis of the center of gravity in the MAS-NMR spectra. H-Al,Ga-offretites produced by ammonium exchange and subsequent calcination reveal evidence of partial demetallation of the framework with formation of extra-lattice metal species. PMID:9477445

Wölker, A; Hudalla, C; Eckert, H; Auroux, A; Occelli, M L

1997-12-01

351

Synthesis and characterization of electrospun gallium nitride nanofibers  

NASA Astrophysics Data System (ADS)

The simple and inexpensive technique of electrospinning was used for the production of long GaN nanofibers. The fibers were made using a precursor solution composed of pure Gallium Nitrate dissolved in dimethylacetamide (DMA) and a viscous solution of Cellulose acetate dissolved in a mixture of DMA and acetone. Using a tube furnace, they were sintered under a Nitrogen atmosphere to decompose the polymer and to reduce Oxygen contamination. This process was followed by sintering under a NH3 flow to complete the synthesis of wurtzite GaN. XRD, ESEM, and FTIR analysis were used to verify the chemical and structural composition of the samples. The I-V characteristics of a device constructed using a single GaN nanofiber showed the formation of ohmic contacts.

Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago-Avilés, Jorge J.

2009-08-01

352

Raman spectroscopy and structure of crystalline gallium phosphide nanowires.  

PubMed

Gallium phosphide nanowires with a most probable diameter of approximately 20.0 nm and more than 10 microns in length have been synthesized by pulsed laser vaporization of a heated GaP/5% Au target. The morphology and microstructure of GaP nanowires have been investigated by scanning electron microscopy and transmission electron microscopy. Twins have been observed along the crystalline nanowires, which have a growth direction of [111]. Raman scattering shows a 4 cm-1 downshift of the longitudinal optical phonon peak in the nanowire with respect to the bulk; the transverse optical phonon frequency and line width are, however, the same as in the bulk. The quantum confinement model first proposed by Richter et al. cannot explain the observed behavior of the Raman modes. PMID:14598449

Xiong, Qihua; Gupta, R; Adu, K W; Dickey, E C; Lian, G D; Tham, D; Fischer, J E; Eklund, P C

2003-08-01

353

Sol-gel synthesis and characterization of yttrium gallium garnets  

NASA Astrophysics Data System (ADS)

Precursor powders for yttrium gallium garnet (Y3Ga5O12, YGG) were prepared by a simple sol-gel method based on the formation of metal chelates in aqueous solvents. A systematic study of sol-gel technique synthesized YGG samples is presented using different complexing agents. Six high-purity organic substances were used as complexing agents, namely, tartaric acid, 1,2-ethanediol, citric acid, ethylene diamine tetra-acetic acid (EDTA), malonic acid, and oxalic acid. These agents were found to influence the characteristics of the end products, in particular their homogeneity. The phase purity, composition, and microstructure of the polycrystalline samples were studied by thermoanalytical methods (TGADTA), x-ray diffraction (XRD) analysis, IR spectroscopy, and scanning electron microscopy (SEM). From the typical XRD patterns of different synthesis products it is concluded that only the use tartaric acid, 1,2-ethanediol, citric acid, and EDTA yields a single YGG phase.

Leleckaite, Asta; Urbonaite, Sigita; Tõnsuaadu, Kaia; Kareiva, Aivaras

2005-08-01

354

Results from the Soviet-American gallium experiment  

SciTech Connect

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of {sup 71}Ge atoms extracted from thirty tons of gallium was measured in five runs during the period of January to July 1990. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20 + 15/{minus}20 (stat) {plus_minus} 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model.

Abazov, A.I.; Anosov, O.L.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.V.; Pshukov, A.M.; Revzin, N.E.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zatsepin, G.T. [AN SSSR, Moscow (USSR). Inst. Yadernykh Issledovanij; Bowles, T.J.; Cleveland, B.T.; Elliott, S.R.; O`Brien, H.A.; Wark, D.L.; Wilkerson, J.F. [Los Alamos National Lab., NM (United States); Davis, R. Jr.; Lande, K. [Pennsylvania Univ., Philadelphia, PA (United States); Cherry, M.L. [Louisiana State Univ., Baton Rouge, LA (United States); Kouzes, R.T. [Princeton Univ., NJ (United States)

1991-12-31

355

Results from the Soviet-American gallium experiment  

SciTech Connect

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of {sup 71}Ge atoms extracted from thirty tons of gallium was measured in five runs during the period of January to July 1990. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20 + 15/{minus}20 (stat) {plus minus} 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model.

Abazov, A.I.; Anosov, O.L.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.V.; Pshukov, A.M.; Revzin, N.E.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zatsepin, G.T. (AN SSSR, Moscow (USSR). Inst. Yadernykh Issledovanij); Bowles, T.J.; Cleveland, B.T.; Elliott, S.R.; O'Brien, H.A.; Wark, D.L.; Wilkerson, J.F.

1991-01-01

356

Single event upsets in gallium arsenide dynamic logic  

SciTech Connect

The advantages and disadvantages of using gallium arsenide (GaAs) dynamic logic in computers and digital systems are briefly discussed, especially with respect to space applications. A short introduction to the topology and operation of GaAs Two-Phase Dynamic FET Logic (TDFL) circuits is presented. Experiments for testing the SEU sensitivity of GaAs TDFL, using a laser to create charge collection events, are described. Results are used to estimate the heavy-ion, soft error rate for TDFL in a spacecraft in geosynchronous orbit, and the dependence of the SEU sensitivity on clock frequency, clock voltage, and clock phase. Analysis of the data includes a comparison between the SEU sensitivities of TDFL and the more common static form of GaAs logic, Directly Coupled FET Logic (DCFL). This is the first reported SEU testing of GaAs dynamic logic.

Fouts, D.J. (Naval Postgraduate School, Monterey, CA (United States). ECE Dept.); Weatherford, T. (SFA Inc., Landover, MD (United States)); McMorrow, C.; Melinger, J.S.; Campbell, A.B. (Naval Research Lab., Washington, DC (United States))

1994-12-01

357

Magnetism driven by surface dangling bonds in gallium nitride nanoclusters  

NASA Astrophysics Data System (ADS)

Magnetic properties of gallium nitride (GaN) semiconductor nanoclusters (NCs) of different sizes were systematically studied by using first-principles calculations. It is observed that the pure GaN NCs can be magnetic even without magnetic elements doping. Similar to the observed magnetism in undoped oxide NCs, the magnetism of the undoped GaN NCs is attributed to the spin polarization of the dangling bond electrons of the 2-coordinate surface nitrogen anions and originates from the spatially localized nature of the dangling bond states and associated on-site Hubbard interaction. It is demonstrated that the magnetism driven by the surface dangling bonds can be suppressed or enhanced via hydrogen passivation or structural design. These results indicate that it is promising to combine the surface magnetism of the GaN NCs with their unique optical properties to fabricate nanosized magneto-optical devices.

Zhao, X. G.; Tang, Z.; Hu, W. X.

2013-02-01

358

Recrystallization of amorphous gallium arsenide by ion beams  

SciTech Connect

An 11-MV arsenic beam was used to amorphize approximately 3.9 ..mu..m of GaAs surface layer at liquid nitrogen temperature. It was found that apparently amorphous gallium arsenide can be reconverted to single crystal by subsequent implantation at higher temperature. The recrystallization by the ion beam proceeded simultaneously from the amorphous surface and the deep amorphous/crystalline interface. Growth of dendrites and/or microtwins occurred at the recrystallizing interfaces. From the comparison of the nuclear stopping curve with the damage distribution in cross-sectional transmission electron micrograph, the threshold value for converting crystalline GaAs into amorphous GaAs was measured to be between 2--5 x 10/sup 20/ keV cm/sup -3/.

Sadana, D.K.; Choksi, H.; Washburn, J.; Byrne, P.F.; Cheung, N.W.

1984-02-01

359

Experimental study on SPDT machining of Gallium Phosphide  

NASA Astrophysics Data System (ADS)

Gallium Phosphide (GaP) is widely used semiconductor material, but can be also used as a material for visible and infrared optical elements. Combination of its optical and mechanical properties such as high mechanical durability, transparency from visible to infrared wavelengths and high refractive index makes it very interesting material for design of high performance optical systems in NIR and MWIR. Manufacturing of optical elements for such wavelength ranges is shifting from traditional grinding and polishing techniques to a more versatile SPDT machining. It is therefore useful to employ SPDT in production of optical surfaces on GaP. As the GaP is similar to GaAs, but harder and more brittle, all all the problems already known for GaAs are present. Here we report results of experiments with SPDT machining of optical surfaces on GaP substrates and comparison with classical machining methods.

Vaclavík, J.; Dole?ek, R.; Lédl, V.; Psota, P.

2013-09-01

360

Coated gallium arsenide neutron detectors : results of characterizationmeasurements.  

SciTech Connect

Effective detection of special nuclear materials (SNM) is essential for reducing the threat associated with stolen or improvised nuclear devices. Passive radiation detection technologies are primarily based on gamma-ray detection and subsequent isotope identification or neutron detection (specific to neutron sources and SNM). One major effort supported by the Department of Homeland Security in the area of advanced passive detection is handheld or portable neutron detectors for search and localization tasks in emergency response and interdiction settings. A successful SNM search detector will not only be able to confirm the presence of fissionable materials but also establish the location of the source in as short of time as possible while trying to minimize false alarms due to varying background or naturally occurring radioactive materials (NORM). For instruments based on neutron detectors, this translates to detecting neutrons from spontaneous fission or alpha-n reactions and being able to determine the direction of the source (or localizing the source through subsequent measurements). Polyethylene-coated gallium arsenide detectors were studied because the detection scheme is based on measuring the signal in the gallium arsenide wafers from the electrical charge of the recoil protons produced from the scattering of neutrons from the hydrogen nucleus. The inherent reaction has a directional dependence because the neutron and hydrogen nucleus have equivalent masses. The assessment and measurement of polyethylene-coated gallium arsenide detector properties and characteristics was the first phase of a project being performed for the Department of Homeland Security and the results of these tests are reported in this report. The ultimate goal of the project was to develop a man-portable neutron detection system that has the ability to determine the direction of the source from the detector. The efficiency of GaAs detectors for different sizes of polyethylene layers and different angles between the detector and the neutron source were determined. Preliminary measurements with a neutron generator based on a deuterium-tritium reaction ({approx}14 MeV neutrons) were performed and the results are discussed. This report presents the results of these measurements in terms of efficiency and angular efficiency and compares them to Monte Carlo calculations to validate the calculation scheme in view of further applications. Based on the results of this study, the polyethylene-coated gallium arsenide detectors provide adequate angular resolution based on proton recoil detection from the neutron scattering reaction from hydrogen. However, the intrinsic efficiency for an individual detector is extremely low. Because of this low efficiency, large surface area detectors ( or a large total surface area from many small detectors) would be required to generate adequate statistics to perform directional detection in near-real time. Large surface areas could be created by stacking the detector wafers with only a negligible attenuation of source neutrons. However, the cost of creating such a large array of GaAs is cost-prohibitive at this time.

Klann, R. T.; Perret, G.; Sanders, J.

2006-09-29

361

Kinetically controlled growth of gallium on stepped Si (553) surface  

NASA Astrophysics Data System (ADS)

Kinetically controlled growth of gallium (Ga) metal has been reported on high index stepped Si (553) surface and its thermal stability with various novel superstructural phases has been analyzed. Auger electron spectroscopy studies revealed that the adsorption of Ga at room temperature (RT) follows Frank–van der Merwe (FM) growth mode while for higher substrate temperature, Ga adsorption remains within the submonolayer range. Thermal desorption and low energy electron diffraction studies investigated the formation of thermally stable Ga-islands and the various Ga induced superstructural phase on Si (553). During room temperature adsorption, (1 1 1)7 × 7 facet of Si (553) reconstructed into (1 1 1)6 × 6 facet while during desorption process, stable (1 1 1)6 × 6 and (1 1 1)?3 × ?3-R30° surface reconstructions has been observed.

Kumar, Mukesh; Pasha, Syed Khalid; Govind

2013-10-01

362

Study of Magnetohydrodynamic Surface Waves on Liquid Gallium  

SciTech Connect

Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.

Hantao Ji; William Fox; David Pace; H.L. Rappaport

2004-05-13

363

Amorphous metal alloys produced by mechanical alloying  

Microsoft Academic Search

Mechanical alloying is a powder metallurgy method used in commercial production of high temperature superalloys. Under specific conditions, mechanical alloying allows the synthesis of amorphous metal alloys from mixtures of pure metal powders or from the powders of intermetallic compounds. Because the amorphizing transformation during mechanical alloying is a solid state reaction, most of the difficulties related to the amorphization

T. J. Tiainen; R. B. Schwarz

1989-01-01

364

[Is it useful to perform a (67)gallium scintigraphy in the follow-up of patients with gastric lymphoma?].  

PubMed

Gastric (67)gallium uptake in patients with peptic ulcer has been described in many publications literature. We present the case of a jejunal (67)gallium uptake in a patient with a background of total gastrectomy due to a diffuse large B cell gastric lymphoma, associated to benign peptic ulcer which had been identified by endoscopy. We have not found any similar cases in regards to (67)gallium reported in the literature. This study aims to present a review of the causes of gastrointestinal uptake of (67)gallium and of the utility of the radiotracer in patients with gastric lymphoma. PMID:11181327

Ruiz Hernández, G; Pallardó-Calatayud, J; Ferrer Albiach, C; Balaguer-Martínez, J V; Romero-de-Avila, C; Castillo-Pallarés, F J

2001-02-01

365

Influence of novel gallium complexes on the homeostasis of some biochemical and hematological parameters in rats.  

PubMed

The aim of this study was to detect possible homeostasis changes in some biochemical and hematological parameters after the administration of gallium (Ga) complexes C (24) and C (85) on an experimental animal model (Wistar strain rats). In order to observe chronobiological aspects, a morning (m) and an evening (e) animal series were constituted. Further on, each series were divided into three groups: control (C), experimental I (EI), and experimental II (EII). Both Ga complexes were solubilized in a carrier solution containing polyethylene glycol (PEG) 400, water, and ethanol. Animals of the C groups received the carrier solution by intraperitoneal injection, those from the EI groups received the solubilized C(24) gallium complex, and those of the EII groups received the solubilized C(85) gallium complex. At the end of the experiment, blood and tissue samples were taken and the following parameters were determined: serum concentration of the nonprotein nitrogenous compounds (uric acid, creatinine, and blood urea nitrogen), hematological parameters (erythrocytes, hemoglobin, leukocytes, and platelets), and the kidney tissue concentration of three essential trace elements (Fe, Cu, and Zn). With the exception of uric acid, the results revealed increased concentrations of the nonprotein nitrogenous compounds both in the morning and in the evening experimental groups. Hematological data showed increased levels of erythrocytes, hemoglobin, and leukocytes and decreased platelet levels in the experimental group given the C(24) gallium complex in the morning (EI-m) group; increased levels of leukocytes and decreased levels of the other parameters in the experimental group given the C(24) gallium complex in the evening (EI-e) group; and increased levels of all hematological parameters in the experimental groups receiving the C(85) gallium complex in the morning (EII-m) group and in the evening (EII-e) group. Decreased kidney tissue concentrations of metals were found in all the experimental groups. Fe levels were significantly decreased in the EI-m receiving the C(24) gallium complex and EII-m which received the C(85) gallium complex and in the EII-e group which received the C(85) gallium complex. In the EI-e group which received the C(24) gallium complex, a significant decrease of Cu concentration was reported. PMID:23990509

Gârban, Gabriela; Silaghi-Dumitrescu, Radu; Ioni??, Hortensia; Gârban, Zeno; H?d?rug?, Nicoleta-Gabriela; Ghibu, George-Daniel; Balt?, Cornel; Simiz, Florin-Dan; Mitar, Carmen

2013-08-30

366

Material and device studies for the development of gallium nitride heterojunction bipolar transistors by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Due to its unique physical properties, gallium nitride (GaN) is under intense investigation for the development of transistors for high power, high frequency and high temperature applications. The majority of existing literature addresses field effect transistors. This dissertation addresses a wide spectrum of materials and device studies required for the development of GaN-based heterojunction bipolar transistors (HBTs). The investigated structure has the emitter region based on n-Al xGa1-xN alloys, while the base and collector were based on p-InyGa1-yN and n-GaN, respectively. The growth and doping of the various layers of the transistor structure, on sapphire substrate, GaN-templates and free standing GaN substrates are addressed. Particular emphasis was placed on the p-type doping of the AlGaN and InGaN alloys with magnesium, both doping of bulk films as well as superlattices. The experimental results were compared with theoretical predictions of a self-consistent solution to the one-dimensional poisson and schrodinger equations. A hole concentration for p-InGaN of 9x1018CM-3 was obtained, which is the highest value published. The device aspect of this research addressed issues related to the development of novel methods of selective growth by molecular beam epitaxy (MBE) of the emitter onto the base. This was found to be necessary to avoid damage of the base during mesa etching. The final product of this research was the fabrication and DC characterization of HBT devices. This included various lithography, metallization, etching and annealing steps. The devices were evaluated under common base and common emitter configurations and the best result obtained was a room temperature gain of 59.

Li, Wei

367

Pulmonary gallium uptake in rats with granulomatosis induced by complete Freund adjuvant  

SciTech Connect

To investigate the mechanism of gallium-67 uptake in lung granulomatosis, we studied 13 rats in which lung granulomatosis was induced by injection of complete Freund adjuvant (CFA) and 14 controls. Gallium uptake was assessed in bronchoalveolar lavage fluid and lavaged lung. The cells responsible for gallium uptake were identified by latent image activation autoradiography. Gallium activity in both lavaged lungs and bronchoalveolar cells (BAC) was higher in CFA-treated animals than in controls (172,205 +/- 134,783 DPM versus 44,456 +/- 14,486 DPM +/- SD (p less than 0.05) and 40,083 +/- 16,350 DPM versus 9100 +/- 4114 DPM (p less than 0.05), respectively). In control rats, about two-thirds of total lung gallium was located in the interstitium, whereas in CFA-treated rats it was found in the mononuclear cells of lung granulomas. Gallium tracks were more numerous in the alveolar macrophages (AM) of CFA-treated rats than in control AM (28.4 +/- 10.0/field versus 8.4 +/- 3.8/field, p less than 0.001) but the number of tracks was proportional to the number of AM (52.4 +/- 18.7 versus 12.2 +/- 4.3, respectively; p less than 0.001). It is concluded that in rats with CFA-induced lung granulomatosis 1) pulmonary gallium uptake increases, 2) mononuclear cells are responsible for this uptake in both granulomas and AM, and 3) the increased uptake is due to the increased number of mononuclear cells.

Stanislas-Leguern, G.; Masse, R.; Jaubert, F.; Chretien, J.; Huchon, G.

1988-01-01

368

Antitumor efficacy and tolerability of systemically administered gallium acetylacetonate-loaded gelucire-stabilized nanoparticles.  

PubMed

The widespread clinical success with most gallium compounds in cancer therapy is markedly hampered by lack of tumor specific accumulation, poor tumor permeability and undesirable toxicity to healthy tissues. The aim of this work was to investigate for the first time antitumor mechanism of a new gallium compound (gallium acetylacetonate; GaAcAc) while assessing effectiveness of gelucire-stabilized nanoparticles (NPs) for potential application in gallium-based lung cancer therapy. NPs loaded with GaAcAc (Ga-NPs) were prepared using mixtures of cetyl alcohol with Gelucire 44/14 (Ga-NP-1) or Gelucire 53/13 (Ga-NP-2) as matrix materials. Of special note from this work is the direct evidence of involvement of microtubule disruption in antitumor effects of GaAcAc on human lung adenocarcinoma (A549). In-vivo tolerability studies were based on plasma ALT, creatinine levels and histopathological examination of tissues. The superior in-vivo antitumor efficacy of Ga-NPs over GaAcAc was depicted in marked reduction of tumor weight and tumor volume as well as histological assessment of excised tumors. Compared to free GaAcAc, Ga-NPs showed a 3-fold increase in tumor-to-blood gallium concentrations with minimized overall exposure to healthy tissues. Overall, enhancement of antitumor effects of GaAcAc by gelucire-stabilized NPs coupled with reduced exposure of healthy tissues to gallium would likely ensure desired therapeutic outcomes and safety of gallium-based cancer treatment. PMID:23858967

Wehrung, Daniel; Bi, Lipeng; Geldenhuys, Werner J; Oyewumi, Moses O

2013-06-01

369

High Performance Titanium Alloys.  

National Technical Information Service (NTIS)

Original titanium alloys appropriate for various uses have been developed. A cost effective corrosion resistant Ti alloy was developed utilizing small effective addition of 0.05% Pd. High strength and high toughness alpha + Beta alloys were developed by t...

M. Okada W. Takahashi T. Maeda Y. Shida T. Fukuda

1990-01-01

370

Role of oxidative stress in the induction of metallothionein-2A and heme oxygenase-1 gene expression by the antineoplastic agent gallium nitrate in human lymphoma cells.  

PubMed

The mechanisms of action of gallium nitrate, an antineoplastic drug, are only partly understood. Using a DNA microarray to examine genes induced by gallium nitrate in CCRF-CEM cells, we found that gallium increased metallothionein-2A (MT2A) and heme oxygenase-1 (HO-1) gene expression and altered the levels of other stress-related genes. MT2A and HO-1 were increased after 6 and 16 h of incubation with gallium nitrate. An increase in oxidative stress, evidenced by a decrease in cellular GSH and GSH/GSSG ratio, and an increase in dichlorodihydrofluorescein (DCF) fluorescence, was seen after 1-4 h of incubation of cells with gallium nitrate. DCF fluorescence was blocked by the mitochondria-targeted antioxidant mitoquinone. N-Acetyl-L-cysteine blocked gallium-induced MT2A and HO-1 expression and increased gallium's cytotoxicity. Studies with a zinc-specific fluoroprobe suggested that gallium produced an expansion of an intracellular labile zinc pool, suggesting an action of gallium on zinc homeostasis. Gallium nitrate increased the phosphorylation of p38 mitogen-activated protein kinase and activated Nrf-2, a regulator of HO-1 gene transcription. Gallium-induced Nrf-2 activation and HO-1 expression were diminished by a p38 MAP kinase inhibitor. We conclude that gallium nitrate induces cellular oxidative stress as an early event which then triggers the expression of HO-1 and MT2A through different pathways. PMID:18586083

Yang, Meiying; Chitambar, Christopher R

2008-06-14

371

Boron alloy  

SciTech Connect

This paper describes a ferro-boron alloy produced in situ in a basic oxygen furnace, an induction furnace, or an electric furnace, or in combination with a mixing vessel. It comprises: 1.4% to 15% by weight boron; less than 0.002% by weight nitrogen; less than about 0.2% by weight carbon; less than about 0.01% by weight aluminum; and the balance iron with minute amounts of residuals.

Sussman, R.C.; Evans, L.G.

1990-06-26

372

Gallium in Feldspar Minerals - an Underutilized Source of Petrogenetic Information  

NASA Astrophysics Data System (ADS)

The trace element gallium is routinely analyzed in all kind of rocks. Regardless of this fact it is rarely used as a petrogenetic indicator element. Arguably the best known exception is the discrimination of A-type granites according to the Ga/Al value. Interpreting these data requires our understanding of how Ga is distributed between coexisting crystal phases and liquids. Because of the great importance of the feldspar minerals for the geochemical evolution of Ga a two- step method for Ga analysis of feldspar minerals using the electron microprobe was developed. The first step includes a screening for increased Ga-values during the routine feldspar analyses. A threshold of 100 ppm Ga was used to define 'Ga-rich feldspars'. These feldspars were analyzed for Ga using a special routine with optimized conditions for trace element analysis. To minimize the well known effects of diffusion of alkaline metals and to maintain the high spatial resolution an accelerating voltage of 15 kV was used. In order to improve precision and the lower detection limit long peak counting times of 360 - 600 seconds were chosen. The background curvature and possible interferences of both Ga-K? and Ga-L? lines were studied using standards very poor in gallium. The influence of the beam current on the stability of different feldspar types was tested. In order to ensure the integrity of the sample and the compliance of the analytical task an optimal ratio of beam current to beam diameter has to be chosen for every analysis. Using optimal conditions with low spatial resolution a lower detection limit of 33 ppm was reached. Using this two-step method we found unexpected high Ga values in feldspars of different rock types. Characteristic examples are albite with a Ga-Ca - ratio of > 1 from albite granites in the Central Eastern Desert (Egypt) and zoned plagioclase from mafic microgranular enclaves in granites formed by magma mixing (Karkonosze Mountains in Poland) with Ga-contents greater than 1000 ppm.

Renno, A. D.

2007-12-01

373

Recent experiments with liquid gallium cooling of crystal diffraction optics  

SciTech Connect

The x-ray beams for the next generation of synchrotrons will contain much more power (1--10 kW) than is available at present day facilities. Cooling the first optical components in these beam lines will require the best cooling technology that one can bring to bear. Argonne continues to pioneer the use of liquid metals as the cooling fluid and has adopted liquid gallium as the liquid metal of choice. Its low melting point, 29.7 {degree}C and its very low vapor pressure make it an easy fluid to handle and its high thermal conductivity and heat capacity make it an excellent cooling fluid. A series of experiments were performed during April 1991 with the wiggler beam at the F2 station of the CHESS facility at Cornell to investigate the cooling of large areas of high power. Two types of cooling crystal geometries were tested. One where the cooling channels were core drilled just below the surface of the crystal and a second where slots were cut into the crystal just below the surface with a diamond saw. Both crystals performed well with photon beam powers up to 1050 W and power densities of up to 14.5 W/mm{sup 2} at normal incidence. An infrared camera was used to measure the variation in the temperature of the top layer of the silicon crystals. For the core-drilled crystal the peak temperature measured at the center of the beam at a power density of 12.3 W/mm{sup 2} was 15 {degree}C hotter than the crystal surface outside of the beam with a flow of liquid gallium of 2 gpm (gallons per minute) and was 10 {degree}C with a flow of 4 gpm. The maximum distortion of the crystal surface distortion of the core-drilled crystal was about {plus minus}2.0 arcsec for the 2 gpm case with a maximum power density of 10.9 W/mm{sup 2} and about 5% of the expected beam intensity was lost at peak power of 14.5 W/mm{sup 2}.

Smither, R.K.; Lee, W.; Macrander, A.; Mills, D.; Rogers, S. (Argonne National Laboratory, Argonne, Illinois 60439 (United States))

1992-02-01

374

(Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon  

DOEpatents

The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Midland, MI)

2001-01-01

375

High-Performance Polymer Light-Emitting Diodes Based on a Gallium-Doped Zinc Oxide\\/Polyimide Substrate  

Microsoft Academic Search

Conducting atomic force microscopy and scanning surface potential microscopy were used to study the surface electrical properties of gallium-doped zinc oxide (GZO) films on the nanoscale. GZO films on a polyimide (PI) substrate were prepared by pulsed laser deposition at various substrate temperatures. Our experimental results show a correlation between the local conductivity and work function (WF) and the gallium

Sy-Hann Chen; Yu-Chyuan Chen

2012-01-01

376

Comparison of the promoting effects of gallium and aluminium on the n -butane isomerization actvity of sulfated zirconia  

Microsoft Academic Search

Sulfated zirconia catalysts promoted by gallium or aluminium were prepared and tested for n-butane isomerization. Both elements increase and stabilize the isomerization rate. Characterization results showed that the\\u000a promoting mechanism of gallium was different from that of aluminium.

Chong-Jiang Cao; Xi-Zhi Yu; Chang-Lin Chen; Nan-Ping Xu; Yan-Ru Wang; Chung-Yuan Mou

2004-01-01

377

Point Defects, Diffusion Mechanisms, and Superlattice Disordering in Gallium Arsenide-Based Materials. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

This paper reviews recent progresses in our understanding of the mechanisms of Gallium self diffusion and impurity diffusion in GaAs, and of the disordering of GaAs/AlGaAs superlattices. Gallium self diffusion and Al-Ga interdiffusion under intrinsic and ...

T. Y. Tan U. Goesele S. Yu

1991-01-01

378

Micro and nano-structured green gallium indium nitride/gallium nitride light-emitting diodes  

NASA Astrophysics Data System (ADS)

Light-emitting diodes (LEDs) are commonly designed and studied based on bulk material properties. In this thesis different approaches based on patterns in the nano and micrometer length scale range are used to tackle low efficiency in the green spectral region, which is known as “green gap”. Since light generation and extraction are governed by microscopic processes, it is instructive to study LEDs with lateral mesa sizes scaled to the nanometer range. Besides the well-known case of the quantum size effect along the growth direction, a continuous lateral scaling could reveal the mechanisms behind the purported absence of a green gap in nanowire LEDs and the role of their extraction enhancement. Furthermore the possibility to modulate strain and piezoelectric polarization by post growth patterning is of practical interest, because the internal electric fields in conventional wurtzite GaN LEDs cause performance problems. A possible alternative is cubic phase GaN, which is free of built-in polarization fields. LEDs on cubic GaN could show the link between strong polarization fields and efficiency roll-off at high current densities, also known as droop. An additional problem for all nitride-based LEDs is efficient light extraction. For a planar GaN LED only roughly 8% of the generated light can be extracted. Novel lightextraction structures with extraction-favoring geometry can yield significant increase in light output power. To investigate the effect of scaling the mesa dimension, micro and nano-sized LED arrays of variable structure size were fabricated. The nano-LEDs were patterned by electron beam lithography and dry etching. They contained up to 100 parallel nano-stripe LEDs connected to one common contact area. The mesa width was varied over 1 ?m, 200 nm, and 50 nm. These LEDs were characterized electrically and optically, and the peak emission wavelength was found to depend on the lateral structure size. An electroluminescence (EL) wavelength shift of 3 nm towards smaller values was observed when the stripe width was reduced from 1 ?m to 50 nm. At the same time a strong fourfold enhancement of the light emission from the patterned region over the unpatterned area was observed. Micro-patterned LEDs showed non-linear scaling of the light output power, and an enhancement of 39 % was achieved for structures with an area fill ratio of 0.5 over an LED with square mesa. Growth of cubic GaN and cubic GaInN/GaN LEDs was shown by M-OVPE in Vshaped grooves formed by the {111} planes of etched silicon. SEM images of the GaN layer in small ( 0.5 ?m) regions show a contrast change where the phase boundary between cubic and wurtzite GaN is expected to occur. The growth parameter space is explored for optimal conditions while minimizing the alloying problem for GaN growth on Si. The cubic GaN phase is confirmed by electron back-scatter diffraction (EBSD) in the V-groove center, whereas wurtzite GaN is found near the groove edges. Luminescence of undoped GaN and GaInN/GaN multi-quantum well structures was studied by cathodoluminescence (CL). The undoped cubic GaN structure showed strong band-edge luminescence at 385 nm (3.22 eV) at 78 K, whereas for the MQW device strong emission at 498 nm is observed, even at room temperature. Full cubic LED structures were grown, and wavelength-stable electroluminescence at 489 nm was demonstrated. LEDs with integrated light extraction structures are grown on free-standing GaN substrates with different off-cut angles. The devices with different off-cut show pronounced features at the top surface that also penetrate the active region. For a 2.24° off-cut, these features resemble fish scales, where the feature sizes are in the ?m-range. The 2.24° off-cut LED shows a 3.6-fold increased light output power compared to a LED on virtually on-axis substrate with 0.06° off-cut. The enhancement found in the fish scale LEDs is attributed to increased light scattering, effectively reducing the fraction of trapped light. These results show the potential of structures on the micro and nanometer scale

Stark, Christoph J. M.

379

Decomposition of trimethylgallium on the gallium-rich GaAs (100) surface: Implications for atomic layer epitaxy  

SciTech Connect

The decomposition of trimethylgallium (TMGa) on the gallium-rich (4{times}6) and (1{times}6) GaAs (100) surface was studied with temperature programmed desorption, Auger electron spectroscopy, and low-energy electron diffraction. TMGa was found to dissociatively chemisorb on the gallium-rich surfaces, apparently at the gallium vacancies that exist on these surfaces. We have unambiguously identified methyl radicals desorbing from the surface with the maximum rate at {similar to}440 {degree}C following a saturation TMGa exposure. Since TMGa was shown to decompose on the clean, gallium-rich GaAs (100) surfaces, the self-limiting deposition of gallium during atomic layer epitaxy must be due to the presence of surface methyl groups which inhibit further TMGa dissociative chemisorption.

Creighton, J.R.; Lykke, K.R.; Shamamian, V.A.; Kay, B.D. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (USA))

1990-07-16

380

Ion beam deposition of epitaxial germanium and gallium arsenide layers  

NASA Astrophysics Data System (ADS)

The traveler presented an invited paper entitled, Ion Beam Deposition of Epitaxial Germanium and Gallium Arsenide Layers, at the Twelfth Symposium on Ion Sources and Ion-Assisted Technology (ISIAT '89) in Tokyo. During informal conversations at this meeting, the traveler was informed about a new Japanese initiative, sponsored by the Ministry of International Trade and Industry and an industrial consortium, to establish an Ion Engineering Research Center, whose purpose will be to provide sophisticated equipment and technology base for exploring and developing new applications of ion beam processing. The traveler also visited five Japanese laboratories involved in research on ion-solid interactions. Developments in ionized cluster beam (ICB) deposition were emphasized at ISIAT '89 and during visits to Kyoto University, where the ICB technique was pioneered, and to Mitsubishi Electric's Itami Works, where commercial ICB systems are now being produced. Discussions at Osaka University concentrated on the application of focused ion beams for maskless patterning of submicron devices and on recent studies of one-dimensional quantum effects in semiconductor wires. At Hitachi Research Laboratory, basic research on thin-film growth was described, as well as progress toward the development of a variable frequency RF quadrupole accelerator for ion implantation.

Haynes, T. E.

1989-07-01

381

Soft tissue reactions evoked by implanted gallium phosphide.  

PubMed

Neural devices may play an important role in the diagnosis and therapy of several clinical conditions, such as stroke, trauma or neurodegenerative disorders, by facilitating motor and pain control. Such interfaces, chronically implanted in the CNS, need to be biocompatible and have the ability to stimulate and record nerve signals. However, neural devices of today are not fully optimized. Nanostructured surfaces may improve electrical properties and lower evoked tissue responses. Vertical gallium phosphide (GaP) nanowires epitaxially grown from a GaP surface is one way of creating nanostructured electrodes. Thus, we chose to study the soft tissue reactions evoked by GaP surfaces. GaP and the control material titanium (Ti) were implanted in the rat abdominal wall for evaluation of tissue reactions after 1, 6, or 12 weeks. The foreign-body response was evaluated by measuring the reactive capsule thickness and by quantification of ED1-positive macrophages and total cells in the capsule. Furthermore, the concentration of Ga was measured in blood, brain, liver and kidneys. Statistically significant differences were noticed between GaP and Ti at 12 weeks for total and ED1-positive cell densities in the capsule. The chemical analysis showed that the concentration of Ga in brain, liver and kidneys increased during 12 weeks of implantation, indicating loss of Ga from the implant. Taken together, our results show that the biocompatible properties of GaP are worse than those of the well-documented biomaterial Ti. PMID:18801568

Linsmeier, Cecilia E; Wallman, Lars; Faxius, Linda; Schouenborg, Jens; Bjursten, Lars M; Danielsen, Nils

2008-09-17

382

Ab initio study of stoichiometric gallium phosphide clusters.  

PubMed

We have studied the static dipole polarizability of stoichiometric gallium phosphide clusters (Ga(n)P(n) with n=2-5) by employing various ab initio wave function based methods as well as density functional theory/time dependent density functional theory (DFT/TDDFT). The calculation of polarizability within DFT/TDDFT has been carried out by employing different exchange-correlation functionals, ranging from simple local density approximation to an asymptotically correct model potential-statistical average of orbital potential (SAOP) in order to study their influences. The values obtained by using the model potential-SAOP are lower than those obtained by local density approximation and generalized gradient approximation. A systematic analysis of our results obtained using the DFT/TDDFT with several exchange-correlation functionals shows that the values of polarizability obtained within generalized gradient approximation by using Perdew-Burke-Ernzerhof exchange with Lee-Yang-Parr correlation functional and Perdew-Burke-Ernzerhof exchange-correlation functionals are the closest to the corresponding results from Møller-Plesset perturbation theory. We have found that the value of average static dipole polarizability per atom reaches the bulk limit from the above as the size of the clusters increases. PMID:19154029

Kamal, C; Ghanty, Tapan K; Banerjee, Arup; Chakrabarti, Aparna

2009-01-14

383

Low-temperature thermal conductivity of terbium-gallium garnet  

SciTech Connect

Thermal conductivity of paramagnetic Tb{sub 3}Ga{sub 5}O{sub 12} (TbGG) terbium-gallium garnet single crystals is investigated at temperatures from 0.4 to 300 K in magnetic fields up to 3.25 T. A minimum is observed in the temperature dependence {kappa}(T) of thermal conductivity at T{sub min} = 0.52 K. This and other singularities on the {kappa}(T) dependence are associated with scattering of phonons from terbium ions. The thermal conductivity at T = 5.1 K strongly depends on the magnetic field direction relative to the crystallographic axes of the crystal. Experimental data are considered using the Debye theory of thermal conductivity taking into account resonance scattering of phonons from Tb{sup 3+} ions. Analysis of the temperature and field dependences of the thermal conductivity indicates the existence of a strong spin-phonon interaction in TbGG. The low-temperature behavior of the thermal conductivity (field and angular dependences) is mainly determined by resonance scattering of phonons at the first quasi-doublet of the electron spectrum of Tb{sup 3+} ion.

Inyushkin, A. V., E-mail: inyushkin@imp.kiae.ru; Taldenkov, A. N. [Kurchatov Institute, Russian Research Centre (Russian Federation)

2010-11-15

384

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor.  

PubMed

Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2-3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3. PMID:24062830

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe; Verboom, Willem

2013-08-16

385

Process for producing gallium-containing solution from aluminum smelting dust  

SciTech Connect

A process for producing a gallium-containing solution from aluminum smelting dust is described comprising mixing aluminum smelting dust with 5 to 50% by weight of an alkaline flux selected from the group consisting of sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide and mixtures thereof, heating the mixture to a temperature sufficient to roast the mixture without fusing the mixture, leaching the roasted mixture at a temperature of 80/sup 0/C. to 100/sup 0/C. with a mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid and mixtures thereof to preferentially solubilize gallium from other material in the roasted mixture, and filtering the leached mixture to separate the solubilized gallium solution therefrom.

Ikeda, H.; Matsui, S.; Era, A.

1988-02-16

386

Gallium-based thermal interface material with high compliance and wettability  

NASA Astrophysics Data System (ADS)

This study reports a gallium-based thermal interface material (GBTIM) consisting of gallium oxides dispersed uniformly into the 99 % gallium metal. The wettability of GBTIM with other materials is disclosed and compared. The thermal conductivity of GBTIM measured by a computer-controlled Mathis TCi thermal analyzer is ˜13.07 W m-1 K-1 at room temperature, which is significantly higher than that of conventional thermal greases. An experimental facility is described to measure the thermal resistance across the GBTIM under steady-state conditions and the thermal interface resistance is measured as low as 2.6 mm2 kW-1 with a pressure of 0.05 MPa, which is an order lower than that of the best commercialized thermal greases. Further, the GBTIM is formed into a desired shape to enhance thermal transfer, such as semi-liquid paste or thermal pad, which can be cut into a required shape.

Gao, Yunxia; Liu, Jing

2012-06-01

387

Influence of Gallium Sources on Impurity Doping in Gas Source MBE GaAs  

NASA Astrophysics Data System (ADS)

The difference of gallium sources, elemental gallium (Ga) and triethylgallium (TEG) on impurity doping in GaAs grown by gas source MBE using AsH3 gas has been studied. Unintentionally doped GaAs epilayers show p- and n-type conductivities, respectively, with and without a Liq.N2 trap in oil diffusion pump evacuation system when TEG was used as a gallium source. On the other hand, all the GaAs epilayers grown using Ga show p-type conductivity. Si doping efficiency by use of SiH4 gas for the growth using TEG is about 6-times higher than that for growth using Ga. The differences of impurity doping in gas source MBE using TEG and Ga are discussed based on the results of photoluminescence and secondary ion mass spectroscopic measurements.

Misawa, Shunji; Okumura, Hajime; Yoshida, Sadafumi

1987-07-01

388

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor  

PubMed Central

Summary Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3.

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe

2013-01-01

389

Renal gallium accumulation in rats with antibiotic-induced nephritis: clinical implications. Concise communication  

SciTech Connect

To determine the effect of antibiotic-induced nephrotoxicity on the renal accumulation of gallium, groups of ten Sprague-Dawley rats were given intraperitoneal injections of gentamycin, amphotericin, or neomycin for a period of 16 to 21 days. In all cases, mild to moderate nephrotoxicity was documented by one or more of the following parameters: serum creatinine, renal weight, urine volume (renal concentrating ability), light microscopy, and electron microscopy. In none of these cases was the renal accumulation of gallium increased over control values. Consequently, diffuse renal accumulation of gallium in patients with subclinical or mild nephrotoxicity is unlikely to be related to short-term treatment with aminoglycosides or amphotericin. In such cases, the physician should seek some other clinical explanation, such as infection.

Taylor, A.; Nelson, H.; Vasquez, M.; Hollenbeck, J.

1980-07-01

390

67Gallium citrate scintigraphy to assess metastatic spread in a dog with an oral melanoma.  

PubMed

Gallium scintigraphy was used to evaluate therapeutic response in a 10-year-old, male, Dutch sheepdog, suffering from an oral melanoma. Treatment was performed with a combination of carboplatin and hypofractionated radiation. Nineteen weeks after radiation therapy, the left submandibular lymph node was surgically removed because of metastatic disease. Thirty weeks after radiation therapy, 67Gallium scintigraphy was performed to assess for residual disease and metastasis. Increased uptake in the right submandibular lymph node area was noted and identified as a melanoma metastasis on cytology. Surgical excision was performed. Twenty-one weeks later, the dog was euthanased because of advanced pulmonary metastases. This report of a case of oral melanoma illustrates the advantages of 67Gallium scintigraphy in monitoring for the presence of metastatic disease and effectiveness of therapy. PMID:19037892

Liuti, T; de Vos, J; Bosman, T; van de Wiele, C; Grinwis, G C M; van Bree, H; Peremans, K

2008-11-13

391

Accurate quantification of radioactive materials by x-ray fluorescence : gallium in plutonium metal /.  

SciTech Connect

Two XRF specimen preparation methods were investigated for quantifying gallium in plutonium metal. Gallium in plutonium was chosen here as an example for demonstrating the efficacy of wavelength dispersive XRF for quantifying radioactive materials. The steps necessary to handle such materials safely will also be discussed. Quantification of plutonium samples by a well-established aqueous specimen preparation method resulted in relative precision and accuracy values of well less than 1%. As an alternative to the aqueous approach, a dried residue method was studied. Quantification of gallium in samples using this method resulted in relative precision and accuracy values an order of magnitude worse, but the method is faster, safer, and generates less waste than the aqueous process. The specimen preparation details and analysis results using each method will be presented here.

Worley, C. G. (Christopher G.)

2002-01-01

392

Rhenium Alloying of Tungsten Heavy Alloys.  

National Technical Information Service (NTIS)

Alloying experiments have been performed using rhenium additions to a classic 90 mass % tungsten heavy alloy. The mixed powder system was liquid phase sintered to full density at 1500 C in 60 min The rhenium modified alloys exhibited a smaller grain size,...

R. M. German A. Bose G. Jerman

1989-01-01

393

Total neutron scattering investigation of the structure of a cobalt gallium oxide spinel prepared by solvothermal oxidation of gallium metal  

NASA Astrophysics Data System (ADS)

A new solvothermal synthesis route to mixed-metal gallium oxides with the spinel structure has been developed for ternary oxides of ideal composition Ga3?xMxO4?y (M=Co, Zn, Ni). The structure of the novel cobalt gallate produced in this manner, Ga1.767(8)Co0.973(8)O3.752(8), has been determined from total neutron scattering to be a partially defective spinel with mixed-valent cobalt (approximately 25% Co3+ and 75% Co2+) and with vacancies on approximately 6% of oxygen sites. Pair distribution function (PDF) analysis reveals significant local deviations from the average cubic structure, which are attributed to the conflicting coordination preferences of the Co2+ (potential Jahn–Teller distortion) and Ga3+ (Ga off-centring). Reverse Monte Carlo (RMC) modelling supports this conclusion since different metal–oxygen bond-distance distributions are found for the two cations in the refined configuration. An investigation of magnetic properties shows evidence of short-range magnetic order and spin-glass-like behaviour, consistent with the structural disorder of the material.

Playford, Helen Y.; Hannon, Alex C.; Tucker, Matthew G.; Lees, Martin R.; Walton, Richard I.

2013-11-01

394

Total neutron scattering investigation of the structure of a cobalt gallium oxide spinel prepared by solvothermal oxidation of gallium metal.  

PubMed

A new solvothermal synthesis route to mixed-metal gallium oxides with the spinel structure has been developed for ternary oxides of ideal composition Ga3-xMxO4-y (M=Co, Zn, Ni). The structure of the novel cobalt gallate produced in this manner, Ga1.767(8)Co0.973(8)O3.752(8), has been determined from total neutron scattering to be a partially defective spinel with mixed-valent cobalt (approximately 25% Co(3+) and 75% Co(2+)) and with vacancies on approximately 6% of oxygen sites. Pair distribution function (PDF) analysis reveals significant local deviations from the average cubic structure, which are attributed to the conflicting coordination preferences of the Co(2+) (potential Jahn-Teller distortion) and Ga(3+) (Ga off-centring). Reverse Monte Carlo (RMC) modelling supports this conclusion since different metal-oxygen bond-distance distributions are found for the two cations in the refined configuration. An investigation of magnetic properties shows evidence of short-range magnetic order and spin-glass-like behaviour, consistent with the structural disorder of the material. PMID:24141264

Playford, Helen Y; Hannon, Alex C; Tucker, Matthew G; Lees, Martin R; Walton, Richard I

2013-10-18

395

Recovery of gallium and arsenic from GaAs wafer manufacturing slurries  

SciTech Connect

Lapping and polishing slurries from the gallium arsenide (GaAs) wafer manufacturing process were used to develop simple and inexpensive methods for separation and recovery of valuable gallium and toxic arsenic. The lapping slurry, containing GaAs, glycerol, alumina, iron oxide, and water, is treated by a process involving water addition, dissolution of GaAs, mixing, sedimentation, decantation, and evaporation. The polishing slurry, containing GaAs, silica, sodium bicarbonate, sodium hypochlorite and water, is treated simply by a repetitive cycle of adding water, mixing, settling, decanting, and evaporating. After treatment, the slurries contain less than 5 ppm of dissolved arsenic and are considered non-hazardous.

Jadvar, R.; McCoy, B.J. (Univ. of California, Davis (United States)); Ford, B.; Galt, J. (Harris Microwave Semiconductor, Inc., Milpitas, CA (United States))

1991-11-01

396

Thermally induced porous structures in printed gallium coating to make transparent conductive film  

NASA Astrophysics Data System (ADS)

A directly printable gallium-based film with both optically transmissive and electrically conductive properties was proposed and demonstrated. The structures, electrical, and optical behaviors of the film printed on the substrate were experimentally investigated. It was disclosed that the porous structure induced inside the printed gallium film by thermal treatment is the main reason for the significant improvement of optical transmittance. A visible transmittance of 47% with a sheet resistance of 16.17 ?/sq was obtained when the thermal treatment temperature and time are maintained at 400 °C and 40 min, respectively.

Mei, Shengfu; Gao, Yunxia; Li, Haiyan; Deng, Zhongshan; Liu, Jing

2013-01-01

397

Patterns of gallium-67 scintigraphy in patients with acquired immunodeficiency syndrome and the AIDS related complex  

SciTech Connect

Thirty-two patients with AIDS related complex (ARC) or acquired immunodeficiency syndrome (AIDS) underwent /sup 67/Ga scans as part of their evaluation. Three patterns of /sup 67/Ga biodistribution were found: lymph node uptake alone; diffuse pulmonary uptake; normal scan. Gallium-67 scans were useful in identifying clinically occult Pneumocystis carinii pneumonia in seven of 15 patients with ARC who were asymptomatic and had normal chest radiographs. Gallium scans are a useful ancillary procedure in the evaluation of patients with ARC or AIDS.

Bitran, J.; Bekerman, C.; Weinstein, R.; Bennett, C.; Ryo, U.; Pinsky, S.

1987-07-01

398

Controlling the coexistence of structural phases and the optical properties of gallium nanoparticles with optical excitation  

NASA Astrophysics Data System (ADS)

We have observed reversible structural transformations, induced by optical excitation at 1.55 ?m, between the ?, ? and liquid phases of gallium in self-assembled gallium nanoparticles, with a narrow size distribution around 50 nm, on the tip of an optical fiber. Only a few tens of nanowatts of optical excitation per particle are required to control the transformations, which take the form of a dynamic phase coexistence and are accompanied by substantial changes in the optical properties of the nanoparticle film. The time needed to achieve phase equilibrium is in the microsecond range, and increases sharply near the transition temperatures.

MacDonald, K. F.; Fedotov, V. A.; Pochon, S.; Stevens, G.; Kusmartsev, F. V.; Emel'yanov, V. I.; Zheludev, N. I.

2004-08-01

399

Nature of the phase transition in gallium arsenide doped with group-VI elements  

SciTech Connect

The authors measure the molar heat capacity on series of gallium arsenide single crystals doped with tellurium and selenium and grown by the Czochralski method from beneath a flux. A conductive calorimeter was provided with anisotropic bismuth thermocouples for converting the normal thermal flux to a tangential electromagnetic field. Antimony was used as the standard. The relative error of the measurements is 1.5%. It is shown that when the degree of doping of gallium arsenide with group-VI elements is increased, the correlation of the densities of acceptor complexes with a donor-vacancy complex grows and clusters are formed.

Balagurova, E.A.; Grekov, Y.B.; Prudnikova, I.A.; Semikolenova, N.A.; Shlyakov, A.T.

1986-09-01

400

Response of Nerve Cell to Inhibitor Recorded by Aluminium-Gallium-Nitride FET  

Microsoft Academic Search

In this work we report on the recording of extracellular potential of NG108-15 nerve cells as response to diisopropylfluorophosphate\\u000a (DFP) using an open gate aluminium gallium nitride\\/gallium nitride (AlGaN\\/GaN) field effect transistor. The biocompatibility\\u000a study of our GaN materials with NG108-15 nerve cells shows a proliferation rate of about 95%. The DFP was added to the medium\\u000a with and without

Michael Gebinoga; Irina Cimalla; Liele Silveira; Maren Klett; Vadim Lebedev; Florentina Niebelschütz; Oliver Ambacher; Andreas Schober

401

Gallium-SPECT in the detection of prosthetic valve endocarditis and aortic ring abscess  

SciTech Connect

A 52-yr-old man who had a bioprosthetic aortic valve developed Staphylococcus aureus bacteremia. Despite antibiotic therapy he had persistent pyrexia and developed new conduction system disturbances. Echocardiography did not demonstrate vegetations on the valve or an abscess, but gallium scintigraphy using SPECT clearly identified a focus of intense activity in the region of the aortic valve. The presence of valvular vegetations and a septal abscess was confirmed at autopsy. Gallium scintigraphy, using SPECT, provided a useful noninvasive method for the demonstration of endocarditis and the associated valve ring abscess.

O'Brien, K.; Barnes, D.; Martin, R.H.; Rae, J.R. (Department of Diagnostic Radiology, Victoria General Hospital Halifax, Nova Scotia (Canada))

1991-09-01

402

Synthesis of nanoporous spheres of cubic gallium oxynitride and their lithium ion intercalation properties.  

PubMed

Cubic spinel structured gallium oxynitride has been synthesized through the reaction of metallic gallium and water in the presence of organic ethylenediamine. The relative content of the mixed solvent of water and ethylenediamine controls the product morphology and structure. A novel well-defined nanoporous structure has finally been obtained, whose large surface area and peculiar surface chemistry will generate novel physical and chemical properties. As an example, lithium intercalation properties for prospective applications in lithium ion batteries are demonstrated in this work. PMID:20173228

Tang, Chengchun; Bando, Yoshio; Huang, Yang; Zhi, Chunyi; Golberg, Dmitri; Xu, Xuewen; Zhao, Jianling; Li, YangXian

2010-02-22

403

Results of the Gallium-Clad Phase 3 and Phase 4 tasks (canceled prior to completion)  

SciTech Connect

This report summarizes the results of the Gallium-Clad interactions Phase 3 and 4 tasks. Both tasks were to involve examining the out-of-pile stability of residual gallium in short fuel rods with an imposed thermal gradient. The thermal environment was to be created by an electrical heater in the center of the fuel rod and coolant flow on the rod outer cladding. Both tasks were canceled due to difficulties with fuel pellet fabrication, delays in the preparation of the test apparatus, and changes in the Fissile Materials Disposition program budget.

Morris, R.N.

1998-08-01

404

Alloys for prosthodontic restorations  

Microsoft Academic Search

The numbers and types of alloys for prosthodontic restorations have increased dramatically over the past 25 years, making selection of an alloy for a given clinical situation difficult. Factors such as cost, the need for better strength, and worries about alloy corrosion have pressured the alloy market to change significantly. A number of properties—including yield strength, hardness, elastic modulus, microstructural

John C. Wataha

2002-01-01

405

Electrical activation studies of silicon implanted aluminum gallium nitride with high aluminum mole fraction  

NASA Astrophysics Data System (ADS)

This research demonstrates a method for producing highly conductive Si-implanted n-type aluminum gallium nitride (AlxGa1-xN) alloys, and represents a comprehensive analysis of the resulting material's electrical and optical properties as a function of Al mole fraction, anneal temperature, anneal time, and implantation dose. Highly conductive alloys are critical to the fabrication of devices operating in deep UV, high-temperature, high-power, and high-frequency environments, and thus this research is significant in regard to the application of such devices. The AlxGa1-xN wafers of this study, with Al concentrations of 10 to 50%, were implanted at room temperature with silicon ions at energies of 200 keV with doses of 1x1014, 5x1014, and 1x1015 CM-2 and annealed from 1100 to 1350°C for 20 to 40 minutes in flowing nitrogen. Excellent activation was achieved for each of the implanted silicon doses for all of the five Al mole fractions studied, with most activation efficiencies above 90%. These activation efficiencies are the highest reported activations, to the best of my knowledge. The Al0.1Ga0.9N annealed for 40 minutes at 1200°C had electrical activations of 73, 94, and 100% for implanted silicon doses of 1x1014, 5x1014, and 1x1015 cm-2, respectively. Higher activations of 83, 100, and 100% were achieved for the Al0.2Ga0.8N implanted with the same doses and annealed at 1300°C for 20 minutes. These same annealing conditions, of 1300°C for 20 minutes, produced slightly lower activations of 74, 88, and 100% for the Si-implanted Al0.3Ga 0.7N. Exceptional activation efficiencies were obtained for each of the implanted silicon doses in the Al0.4Ga0.6N. The Al0.4Ga0.6N implanted with a dose of 1x1014 cm-2 silicon ions had an activation of 99% following a 20 minute anneal at 1350°C, while the samples implanted with the higher silicon doses of 5x1014 and 1x1015 cm-2 had activations of 100 and 96%, respectively, after being annealed at 1200°C for 40 minutes. The Al0.5Ga0.5N exhibited activation efficiencies of 100, 96, and 66% for the three implanted silicon doses after being annealed at 1300°C for 20 minutes. The mobilities were found to decrease as the Al concentration of the AlxGa1-xN was increased from 10 to 50% and also as the implanted silicon dose was increased. Typical mobilities ranged from 101 cm2/V·s for the Al 0.1Ga0.9N implanted with 1x1014 cm -2 silicon ions to 35 cm2V·s obtained for the Al0.5Ga0.5N implanted with 1x1015 cm -2 silicon ions. The cathodoluminescence results support the electrical results in determining the optimal annealing conditions.

Moore, Elizabeth A.

406

Structure and properties of a Pu-0.18 wt.% Ga alloy  

NASA Astrophysics Data System (ADS)

This study describes the characterisation of a cast plutonium-0.18 wt.% gallium (Pu-0.18 wt.% Ga) alloy, both in the as-cast condition as well as following an homogenising heat treatment. The alloy was subjected to density measurements, differential scanning calorimetry (DSC), dilatometry, optical microscopy, electron probe micro-analysis (EPMA), X-ray diffraction (XRD) and hardness measurements. The Ga content is insufficient to retain a wholly delta phase at ambient temperature. Instead, the alloy appears to be a mixture of alpha- and delta-Pu, which is borne out by density, dilatometry, DSC and XRD. Optical microscopy of the alloy following heat treatment revealed the microstructure to be composed of a two-phase mixture of alpha-Pu (?-Pu) and delta-Pu (?-Pu). EPMA of the heat treated alloy shows the Ga content to be evenly distributed throughout the microstructure. The hardness of the heat treated alloy is approximately 25% lower than that of unalloyed Pu. No evidence supporting the presence of an amorphous Pu phase has been found.

Wheeler, D. W.; Jenkins, R. F. E.; Gover, R. K. B.; Matthews, M. B.; Roussel, P.

2013-09-01

407

Synthesis and Characterization of Electronically Active Materials.  

National Technical Information Service (NTIS)

Contents: Research on III-V compound semiconductors, aluminum phosphide, gallium arsenide, gallium phosphide, Gallium Arsenide-Phosphide Alloys, growth of gallium phosphide from the melt, review of diffusion in gallium arsenide, role of thermal spikes in ...

L. R. Weisberg H. W. Leverenz

1964-01-01

408

Lanthanum Gallium Tin Antimonides LaGaxSnySb2  

NASA Astrophysics Data System (ADS)

A series of quaternary lanthanum gallium tin antimonides LaGaxSnySb2 was elaborated to trace the structural evolution between the known end members LaGaSb2 (SmGaSb2-type) and LaSnySb2 (LaSn0.75Sb2-type). Five members of this series were characterized by single-crystal X-ray diffraction. For low Sn content, the Sn atoms disorder with Ga atoms in zigzag chains to form solid solutions LaGa1-ySnySb2 (0<=y<=0.2) adopting the SmGaSb2-type structure, as exemplified by LaGa0.92(3)Sn0.08Sb2 and LaGa0.80(3)Sn0.20Sb2 (orthorhombic, space group D52-C2221,Z=4). For higher Sn and lower Ga content, there is a segregation in which the Sn atoms appear in chains of closely spaced partially occupied sites as in the parent LaSn0.75Sb2-type structure whereas the Ga atoms remain in zigzag chains as in the parent SmGaSb2-type structure. This feature is observed in the structures of LaGa0.68(4)Sn0.31(3)Sb2, LaGa0.62(3)Sn0.32(3)Sb2, and LaGa0.43(3)Sn0.39(3)Sb2 (orthorhombic, space group D172h-Cmcm,Z=4). The last example illustrates that the combined Ga/Sn content can be substoichiometric (x+y<1). These compounds have a layered nature, with the chains of Ga or Sn atoms residing between 2?[LaSb2] slabs.

Morgan, Mark G.; Wang, Meitian; Mills, Allison M.; Mar, Arthur

2002-08-01

409

Gallium arsenide fast photodetectors: Selection criteria and predicted response  

NASA Astrophysics Data System (ADS)

The main characteristics (sensitivity, response time, dynamic range) of a photoconductive detector (PCD) depend on the intrinsic physical (lattice parameter, extended and local defects) and electrical properties (resistivity, mobility, carrier lifetime) of the material. Selection criteria for semi-insulating undoped gallium arsenide (GaAs) were thoroughly examined for their capacity to select the more suitable material for the fabrication of fast PCDs, used in gamma-ray pulse (E~1.2 MeV, ?FWHM=30 ns) metrology. An analytical model, which assumes that carrier recombination takes place through EL2 type recombination centers [M. O. Manasreh and B. C. Covington, Phys. Rev. B 35, 2524 (1987)], was developed. Taking into account the initial physical and electrical properties of the GaAs material, the model accurately predicts the response of the PCDs after a neutron preirradiation step (dose range: 5×1014 to 1×1016 neutrons/cm2), which was used to optimize the PCD characteristics and in particular to reduce the response time to values lower than 100 ps. This led to the identification and validation of key parameters of the initial properties of single crystal GaAs materials influencing the PCDs final characteristics. Thus, depending on the user defined specifications, GaAs material initial properties and neutron preirradiation dose can be fixed to fabricate GaAs PCDs exhibiting the desired response time, sensitivity, and dynamic range. The study established that the PCDs characteristics are controlled only by the initial GaAs material properties when neutron preirradiation doses remain below 1×1015 neutrons/cm2, whereas they are mainly controlled by neutron induced crystal defects above this dose.

Foulon, F.; Bergonzo, P.; Brullot, B.; Rubbelynck, C.; Flicstein, J.; Petit, P.

2000-09-01

410

Metrology of gallium nitride electronics using micro-Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Possessing a wide band gap and large break down field, gallium nitride (GaN) is of interest for a host of high power, high frequency applications including next generation cellular base stations, advanced military radar, and WiMAX networks. Much of this interest stems from the continued development of the AlGaN/GaN high electron mobility transistor (HEMT) that is capable of operating at sizable power densities and switching speeds. The same fields responsible for this performance, however, also elicit acute device heating and elastic loads. These induced thermomechanical loads limit both performance and reliability thus necessitating continued improvement in the management and characterization of the coupled environments. In response, this study establishes a new implementation of Raman spectroscopy capable of simultaneously measuring the operational temperature and stress in a HEMT using only the Stokes response. First, the linewidth (FWHM) of the Stokes signal is utilized to quantify the operating temperature of a HEMT independent to the influences of stress. Second, a new method, incorporating the use of the linewidth and peak position in tandem, is developed to estimate the biaxial thermoelastic stress that arises during device operation. With this capability, the HEMT's resultant load is assessed, highlighting the large role of the residual stress on the total mechanical state of the device. Subsequently, this same linewidth is leveraged to identify the distinct effect that electrical carriers have on the thermally relevant decay of longitudinal optical phonon modes. Further investigation of the lattice transport then concludes the study by way of an analytical treatment describing the significant influence of interfacial disorder on the energy transport at GaN/substrate boundaries.

Beechem, Thomas E., III

411

Phase-change activities on gallium-doped indium oxide  

NASA Astrophysics Data System (ADS)

This study investigated the phase-change activities on a gallium-doped indium oxide (Ga:InO) device that can be supplied with a constant heat flow via symmetric contact to a pair of rodlike heating elements. A device set/reset current of 0.8/18 ?A and resistance window of 2.6×105 to 107 ? can be found on Ga:InO with a 6.2 ?m2 device area and a thickness of 40 nm. Analysis of a log-log plot revealed slopes of 1.07+/-0.01 and -1.12+/-0.03 that were found to correlate with the switching current and resistance change between the high-/low-value states of the Ga:InO device area, respectively. These observations lead to the estimated energy densities of 1.77+/-0.11 pJ/?m3 and 7.26+/-0.44 pJ/?m3 required to initiate the set and reset process in Ga:InO, respectively. Through differential scanning calorimetry analysis and acceleration tests of the Ga:InO film and the device, an activation energy of ~1.275+/-0.005 eV was found, which corresponded to the high-/low-resistance state change. A data retention time of ten years was further estimated when the Ga:InO device is operated at 75 °C. According to the transmission electron microscopy analysis, these observations are correlated with an amorphous to cubic phase transition in In2O3, which takes place at a crystallization temperature of 252 °C, and suggest that the phase-change activities originate from the Joule heating effect.

Wang, S.-L.; Peng, L.-H.

2010-10-01

412

Temperature and field effects on reflectivity of gallium selenide surface  

NASA Astrophysics Data System (ADS)

Monocrystals of gallium selenide (GaSe) has recently attracted significant attention in the field of new optoelectronic devices, due to the original combination of its specific features such as nonlinear optical properties, layered structure and high-photo sensitivity. GaSe crystals show both high reflectivity and unique surface perfection, which leads to a promising candidate for next generation optical devices. We will present our experimental results of reflection spectra of such crystals for various temperatures (273°K-383°K) and applied electric field (1 V/cm - 20 V/cm). The reflection spectra were analyzed to identify the mechanism of the reflective coefficient change in GaSe as a function of wavelength, temperature and electric field. This study will identify the optimal electrical field regimes and spectral segments, where we experimentally revealed reflective properties of GaSe are suitable for creating the field regulated optical applications of decoder and depolarizer. The temperature dependence of GaSe reflectance spectrum, its temperature and applied field dependences exemplified that the processes of photon-electron inter-exchanging on the surfaces are dominated over the bulk processes in forming the reflectance properties of layered crystals. The perfectness of natural surface and their high reflective properties weren't changed in the interval of experimental temperatures. The monolayer surface of GaSe can be utilized as an easy prepared natural plane surface for new optical devices on their surface basis in their original combinations. Such devises are applicable for optical information processing systems because of the stability function and weak dependence of the function of bulk properties.

Alhasson, Bader; Hajiyev, Yashar; Matin, Mohammad

2008-08-01

413

SPECT gallium-67 scanning in early human immunodeficiency virus (HIV) infection. Failure of scanning abnormalities to correlate with immunologic staging.  

PubMed

The use of gallium scanning in the treatment of patients with AIDS has been well described. In this study, 27 HIV-infected patients (Walter Reed Staging Classification I-V) with normal chest roentgenograms were evaluated to determine the occurrence of thoracic gallium abnormalities in early HIV infection. SPECT was used for gallium scanning. Patients received gallium injection on day 1 and bronchoalveolar lavage on day 2, and scanning was performed on day 3. Twenty-eight scans in 27 patients were performed. Mean nodal SPECT activity was compared with corresponding values for lung parenchyma, bronchoalveolar lavage cell counts, and peripheral blood T4 lymphocyte counts. No relationship between nodal and parenchymal activity and cell counts was observed. Although visual scan interpretation was unaffected, gallium activity was significantly increased in the region of bronchoalveolar lavage compared with uptake in other lung regions. It is concluded that SPECT gallium scanning demonstrates significant gallium avidity in recently lavaged lung areas, although no impact on visual scan interpretation was seen. Further, no correlation was seen between the degree of nodal uptake and the immunologic status of these patients with early HIV infection. PMID:2340670

Anders, G T; Timmons, J H; Johnson, J E; Blanton, H M; Hartshorne, M F

1990-05-01

414

Gallium-cladding compatibility testing plan: Phase 3 -- Test plan for centrally heated surrogate rodlet test. Revision 2  

SciTech Connect

The Fissile Materials Disposition Program (FMDP) is investigating the use of weapons grade plutonium in mixed oxide (MOX) fuel for light-water reactors (LWR). Commercial MOX fuel has been successfully used in overseas reactors for many years; however, weapons derived fuel may differ from the previous commercial fuels because of small amounts of gallium impurities. A concern presently exists that the gallium may migrate out of the fuel, react with and weaken the clad, and thereby promote loss of fuel pin integrity. Phases 1 and 2 of the gallium task are presently underway to investigate the types of reactions that occur between gallium and clad materials. This is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. This Plan summarizes the projected Phase 3 Gallium-Cladding compatibility heating test and the follow-on post test examination (PTE). This work will be performed using centrally-heated surrogate pellets, to avoid unnecessary complexities and costs associated with working with plutonium and an irradiation environment. Two sets of rodlets containing pellets prepared by two different methods will be heated. Both sets will have an initial bulk gallium content of approximately 10 ppm. The major emphasis of the PTE task will be to examine the material interactions, particularly indications of gallium transport from the pellets to the clad.

Morris, R.N.; Baldwin, C.A.; Wilson, D.F.

1998-07-01

415

The reactivity of gallium-(I), -(II) and -(III) heterocycles towards Group 15 substrates: attempts to prepare gallium-terminal pnictinidene complexes.  

PubMed

The reactivity of a series of Ga(I), Ga(II) and Ga(III) heterocyclic compounds towards a number of Group 15 substrates has been investigated with a view to prepare examples of gallium-terminal pnictinidene complexes. Although no examples of such complexes were isolated, a number of novel complexes have been prepared. The reactions of the gallium(I) N-heterocyclic carbene analogue, [K(tmeda)][:Ga{[N(Ar)C(H)](2)}] (Ar = 2,6-diisopropylphenyl) with cyclo-(PPh)(5) and PhN[double bond, length as m-dash]NPh led to the unusual anionic spirocyclic complexes, [{kappa(2)P,P'-(PhP)(4)}Ga{[N(Ar)C(H)](2)}](-) and [{kappa(2)N,C-PhNN(H)(C(6)H(4))}Ga{[N(Ar)C(H)](2)}](-), via formal reductions of the Group 15 substrate. The reaction of the digallane(4), [Ga{[N(Ar)C(H)](2)}](2), with (Me(3)Si)N(3) afforded the paramagnetic, dimeric imido-gallane complex, [{[N(Ar)C(H) ](2)}Ga{mu-N(SiMe(3))}](2), via a Ga-Ga bond insertion process. In addition, the new gallium(III) phosphide, [GaI{P(H)Mes*}{[N(Ar)C(H)](2) }], Mes* = C(6)H(2)Bu(t)(3)-2,4,6; was prepared and treated with diazabicycloundecane (DBU) to give [Ga(DBU){P(H)Mes*}{[N(Ar)C(H)](2)}], presumably via a gallium-terminal phosphinidene intermediate, [Ga{[double bond, length as m-dash]PMes*}{[N(Ar)C(H)](2) }]. The possible mechanisms of all reactions are discussed, all new complexes have been crystallographically characterised and all paramagnetic complexes have been studied by ENDOR and/or EPR spectroscopy. PMID:16357962

Baker, Robert J; Jones, Cameron; Mills, David P; Murphy, Damien M; Hey-Hawkins, Evamarie; Wolf, Robert

2005-10-26

416

Combined effect of gallium and carbon on the structure and magnetic properties of nanocrystalline SmFe9  

NASA Astrophysics Data System (ADS)

SmFe9-yGaxC carbides (0<=x<=1) were prepared by a two-step method of powder high-energy milling with annealing between 873 and 1200 K and a subsequent carbonation with heavy hydrocarbon at 693 K. The x-ray diffraction analysis with the Rietveld technique indicates an anisotropic volume expansion under carbonation slackened by the gallium substitution. The average saturation magnetic moment per Fe atom, measured with an applied field up to 200 kOe, increases slightly to 2.00 µB with Ga content. The Curie temperature, always 15 K above that of the homologous 2/17 carbides, is reduced by a dilution effect with Ga substitution and a concomitant increase of the negative Fe-Fe interactions. The Mössbauer spectra have been analysed on the basis of the binomial law related to the different Fe environments. The hyperfine parameter assignment to each individual crystallographic site was performed according to the correlation between isomer shift and Wigner-Seitz cell volumes calculated with a specific code in the P 1 space group allowing the splitting of the partially occupied atomic positions. The role of the C insertion is shown, on the one hand, by the increase of isomer shift due to the volume expansion with an enhancement of the charge transfer from the rare-earth atoms and, on the other hand, by the hyperfine field increase, pointing out the predominance of the negative core electron polarization term. The coercive field of 27 kOe, combined with a Curie temperature of 680 K, makes the alloy SmFe8.75Ga0.25C promising for further applications in the field of high-performance permanent magnets.

Bessais, L.; Dorolti, E.; Djéga-Mariadassou, C.

2006-04-01

417

Three cases demonstrating the role of gallium scanning in relapsing Hodgkin's disease and non-Hodgkin lymphoma  

SciTech Connect

Restaging of Hodgkin's disease and non-Hodgkin lymphoma for chemotherapy traditionally requires chest radiograph and abdominal computerized tomogram (CT) for routine follow-up examination. Although gallium scanning has had a poor record in the past, recent studies suggest that improved techniques have given this method high sensitivity. We present three cases in which gallium correctly staged lymphoma that had been missed or misinterpreted by chest radiographs and abdominal CT. Gallium imaging is useful in follow-up of lymphoma patients especially when the CT scan is difficult to interpret.

Zollars, L.E.; Nagel, J.S.; Tumeh, S.S.

1987-10-01

418

Direct Observation of Self-Limiting Gallium Deposition on GaAs during Laser-Atomic Layer Epitaxial Processing  

NASA Astrophysics Data System (ADS)

The first real-time observation of the gallium arsenide surface during laser-assisted atomic layer epitaxy (LALE) is presented. Self-limiting decomposition of trimethylgallium (TMG) to gallium on (001) GaAs at temperatures between 340°C-390°C during LALE processing was observed by surface photo-absorption (SPA) measurements. The self-limiting deposition is due to an equilibrium between alkylgallium species arriving at the surface and those desorbing from the surface during simultaneous TMG and laser exposure. When the TMG flow is stopped, the remaining alkyl species desorb from the surface leaving a self-limited deposition of gallium behind.

Simko, Jeffry P.; Meguro, Takashi; Iwai, Sohachi; Ozasa, Kazunari; Hirata, Akira; Aoyagi, Yoshinobu; Sugano, Takuo

1992-11-01

419

Polyaniline\\/gallium doped ZnO heterostructure device via plasma enhanced polymerization technique: Preparation, characterization and electrical properties  

Microsoft Academic Search

The ZnO and gallium-doped ZnO nanoparticles (NPs) were synthesized by simple chemical method and used for the fabrication\\u000a of p-polyaniline\\/n-ZnO heterostructures devices in which polyaniline was deposited by plasma-enhanced polymerization. The\\u000a increment in the crystallite sizes of gallium doped ZnO nanoparticles from ~21.85 nm to ~32.39 nm indicated the incorporation\\u000a of gallium ion into the ZnO nanoparticles. The surface and structural studies

Sadia Ameen; M. Shaheer Akhtar; Young Soon Kim; O-Bong Yang; Hyung-Shik Shin

2011-01-01

420

Gallium arsenide epitaxial growth, volume 2. Citations from the NTIS data base  

NASA Astrophysics Data System (ADS)

Research abstracts on GaAs epitaxial growth in liquid and vapor phases are included in this bibliography. Techniques, tests, physical properties, crystal structure, and doping are described. The use of gallium arsenide in optical modulators, fiber optics, semiconductor diodes, and microwave equipment is cited. This updated bibliography contains 229 abstracts, 45 of which are new entries to the previous edition.

Carrigan, B.

1980-03-01

421

Gallium arsenide epitaxial growth (a bibliography with abstracts). Report for 1964-Oct 1975  

Microsoft Academic Search

Research on GaAs epitaxial growth in liquid and vapor phases is included in this bibliography. Techniques, tests, physical properties, crystal structure and doping are described. Gallium arsenide use in optical modulators, fiber optics, semiconductor diodes and microwave equipment is also discussed. (Contains 172 abstracts) (GRA)

1976-01-01

422

Gallium arsenide epitaxial growth, volume 2. Citations from the NTIS data base  

Microsoft Academic Search

Research abstracts on GaAs epitaxial growth in liquid and vapor phases are included in this bibliography. Techniques, tests, physical properties, crystal structure, and doping are described. The use of gallium arsenide in optical modulators, fiber optics, semiconductor diodes, and microwave equipment is cited. This updated bibliography contains 229 abstracts, 45 of which are new entries to the previous edition.

B. Carrigan

1980-01-01

423

Gallium arsenide epitaxial growth, volume 2. Citations from the NTIS data base  

Microsoft Academic Search

Research abstracts on GaAs epitaxial growth in liquid and vapor phases are included in this bibliography. Techniques, tests, physical properties, crystal structure, and doping are described. Gallium arsenide use in optical modulators, fiber optics, semiconductor diodes and microwave equipment is cited.

M. F. Smith

1978-01-01

424

Gallium arsenide epitaxial growth, volume 1. Citations from the NTIS data base  

Microsoft Academic Search

Research abstracts on GaAs epitaxial growth in liquid and vapor phases are included in this bibliography. Techniques, tests, physical properties, crystal structure, and doping are described. Gallium arsenide use in optical modulators, fiber optics, semiconductor diodes, and microwave equipment is also studied.

M. F. Smith

1978-01-01

425

Value of gallium imaging in the evaluation of tattoo granulomas due to sarcoidosis.  

PubMed

We report the case of a patient who developed granulomas in a ten-year-old tattoo. Total body gallium scanning detected the presence of bilateral hilar adenopathy not apparent on routine chest roentgenograms and thus established a diagnosis of systemic sarcoidosis. PMID:1959427

Colp, C R; Goldfarb, R; Ongseng, F

1991-12-01

426

Backward propagation of light pulse in phthalocyanin gallium PMMA at room temperature  

Microsoft Academic Search

Light speed control had been an interesting issue in recent years. In this work, the authors experimentally observed the backward propagation of light pulse in Phthalocyanin Gallium polymethyl methacrylate (PMMA) at room temperature, firstly. Taking use of the modulation technique, we got the time advancement of 260 mus when the sample length was 2 mm long and the modulation frequency

Hao Wang; Chunguang Zhang

2010-01-01

427

Infected cyst localization with gallium SPECT imaging in polycystic kidney disease  

SciTech Connect

This case report describes a 43-year-old woman with polycystic renal disease and cyst infection. Infected cysts of the left kidney were successfully localized with Ga-67 citrate SPECT imaging and CT. Other imaging, including planar gallium imaging, was helpful diagnostically, but could not determine the exact location of infection within the kidney.

Amesur, P.; Castronuovo, J.J.; Chandramouly, B.

1988-01-01

428

Behavior of excess currents in n-type gallium arsenide tunnel diodes  

Microsoft Academic Search

An investigation was made into the nature of the excess currents in n-type gallium arsenide tunnel diodes and the influence of irradiation with 2.0-MeV electrons on the current-voltage characteristics of the diodes.

A. P. Vyatkin; V. A. Glushchenko; R. P. Parkhomenko; A. P. Pastor

1981-01-01

429

Novel transparent conductors based on molybdenum oxide and gallium doped zinc oxide  

Microsoft Academic Search

The primary aim of the present work is to gain a better understanding of the fundamentals and factors affecting the properties of alternative transparent conducting oxides (TCOs) in order to grow films with controlled properties. The two systems studied here as substitutes for indium tin oxide (ITO) are molybdenum oxide and gallium doped ZnO. The two systems not only offer

Vikram Bhosle

2007-01-01

430

Comparison of Gallium Nitride High Electron Mobility Transistors Modeling in Two and Three Dimensions.  

National Technical Information Service (NTIS)

This thesis looks at modeling Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) Semiconductors. The GaN device has potential future military use in the high power and high frequency operation replacing costly millimeter wave tubes This would ...

W. A. Gibson

2007-01-01

431

Orientation mediated self-assembled gallium phosphide islands grown on silicon  

Microsoft Academic Search

Evolution of gallium phosphide epitaxial islands, grown on the (001), (111), (110) and (113) surfaces of Si by chemical beam epitaxy, has been investigated by p-polarized reflectance spectroscopy, transmission electron microscopy and atomic force microscopy. The growth nucleates as faceted three-dimensional islands on the (001) and (111) Si surfaces because of the polar nature of the heterointerface which increases the

V. Narayanan; S. Mahajan; N. Sukidi; K. J. Bachmann; V. Woods; N. Dietz

2000-01-01

432

Bilateral Comparison of Mercury and Gallium Fixed-Point Cells Using Standard Platinum Resistance Thermometer  

NASA Astrophysics Data System (ADS)

The objective of project EURAMET 1127 (Bilateral comparison of triple point of mercury and melting point of gallium) in the field of thermometry is to compare realization of a triple point of mercury (-38.8344 °C) and melting point of gallium (29.7646 °C) between the Slovenian national laboratory MIRS/UL-FE/LMK and the Croatian national laboratory HMI/FSB-LPM using a long-stem 25 ? standard platinum resistance thermometer (SPRT). MIRS/UL/FE-LMK participated in a number of intercomparisons on the level of EURAMET. On the other hand, the HMI/LPM-FSB laboratory recently acquired new fixed-point cells which had to be evaluated in the process of intercomparisons. A quartz-sheathed SPRT has been selected and calibrated at HMI/LPM-FSB at the triple point of mercury, the melting point of gallium, and the water triple point. A second set of measurements was made at MIRS/UL/FE-LMK. After its return, the SPRT was again recalibrated at HMI/LPM-FSB. In the comparison, the W value of the SPRT has been used. Results of the bilateral intercomparison confirmed that the new gallium cell of the HMI/LPM-FSB has a value that is within uncertainty limits of both laboratories that participated in the exercise, while the mercury cell experienced problems. After further research, a small leakage in the mercury fixed-point cell has been found.

Bojkovski, J.; Veliki, T.; Zvizdi?, D.; Drnovšek, J.

2011-08-01

433

Gallium citrate Ga 67 accumulation in pulmonary lesions after chemotherapy (MOPP)  

SciTech Connect

We have described a patient with Hodgkin's disease who had fever and pulmonary infiltrates after treatment with mantle x-ray therapy and two courses of MOPP. Gallium affinity of the lung lesions proved at biopsy not to be due to Hodgkin's disease, but probably to chemotherapy-induced pulmonary toxicity.

Wells, J.D.; Huskison, W.T.; Davenport, O.L.

1986-10-01

434

Experiment to Test the Viability of a Gallium-Arsenide Cathode in a SRF Electron Gun.  

National Technical Information Service (NTIS)

Strained gallium arsenide cathodes are used in electron guns for the production of polarized electrons. In order to have a sufficient quantum efficiency lifetime of the cathode the vacuum in the gun must be 10(sup -11) Torr or better, so that the cathode ...

A. Burrill D. Pate I. Ben-Zvi J. Kewisch T. Rao

2009-01-01

435

Solubility of indium probe atoms in supercooled gallium liquid metal between 8K and 300K  

NASA Astrophysics Data System (ADS)

Liquid gallium samples were made that remain supercooled down to 8 K. Perturbed angular correlation (PAC) measurements were made over the range 8-293 K to determine nuclear quadrupole interactions at 111In/Cd probe atoms doped into the gallium at the part-per-billion level. Near 295 K, the PAC spectrum exhibits a signal with a constant anisotropy (signal 1) for nearly all Cd probes that is consistent with extreme motional averaging of electric field gradients. This is typical of probe atoms dissolved in liquids. Cooling below 295 K, signal 1 is progressively replaced by a high-frequency, broadly-distributed quadrupole interaction signal (signal 2) that is attributed to probe atoms adhering to bounding walls of the gallium drop. The changes are reversible and attributed to changes in the terminal solubility of solutes in gallium with temperature. The observed fractions of indium in solution were approximately 100% at 295 K, 50% at 283 K, 15% at 140 K and 10% at 73 K.

Yin, Xiangyu; Newhouse, Randal; Bevington, John; Collins, Gary

2010-10-01

436

Layer by layer nanoassembly of copper indium gallium selenium (CIGS) nanoparticles for solar cell application  

Microsoft Academic Search

In this research thesis, copper indium gallium selenium (CIGS) nanoparticles were synthesized from metal chlorides, functionalized to disperse in water, and further used in layer by layer (LbL) nanoassembly of CIGS films. CIGS nanoparticles were synthesized through the colloidal precipitation in an organic solvent. The peak and average sizes of the synthesized particles were measured to be 68 nm and

Azadeh Hemati

2011-01-01

437

Gallium arsenide lasers (a bibliography with abstracts). Report for 1964-nov 79  

SciTech Connect

The report covers the design, development, and applications of gallium arsenide lasers. Studies on band theory, optical modulators, emission spectra, optical pumping, tuning, and efficiency of these lasers are included. (This updated bibliography contains 195 abstracts, 22 of which are new entries to the previous edition.)

Carrigan, B.

1980-01-01

438

Analysis of gallium arsenide deposition in a horizontal chemical vapor deposition reactor using massively parallel computations  

Microsoft Academic Search

A numerical analysis of the deposition of gallium arsenide from trimethylgallium (TMG) and arsine in a horizontal CVD reactor with tilted susceptor and a 3? diameter rotating substrate is performed. The three-dimensional model includes complete coupling between fluid mechanics, heat transfer, and species transport, and is solved using an unstructured finite element discretization on a massively parallel computer. A reaction

Andrew G. Salinger; John N. Shadid; Scott A. Hutchinson; Gary L. Hennigan; Karen D. Devine; Harry K. Moffat

1999-01-01

439

Growth and impurity-trapping kinetics in sulfur-doped gallium arsenide epitaxy  

SciTech Connect

Measurements have been made on the effects of crystallization conditions on the growth rates and electrophysical parameters for sulfur-doped epitaxial gallium arsenide films: gas speed, supersaturation, and deposition temperature. There is a correlation between the impurity concentration and the growth rate. The results are discussed from a model that incorporates interaction between impurity atoms and matrix ones.

Vilisova, M.D.; Lavrent'eva, L.G.; Porokhovnichenko, L.P.; Chernov, N.A.

1988-07-01

440

Electrical and electron microscope studies of the annealing of tellurium-doped gallium arsenide  

Microsoft Academic Search

Hall effect measurements and electron microscope examination of tellurium-doped gallium arsenide crystals annealed at various temperatures indicate that tellurium and copper (present as a contaminant) produce a high population of matrix point defects which are probably simple vacancies. Annealing at temperatures below 1000°C causes the growth of intrinsic prismatic vacancy loops on {111} and {100} planes in association with decorations

D. Laister; G. M. Jenkins

1971-01-01

441

A mobility study of the radiation induced order effect in gallium arsenide  

SciTech Connect

N-type gallium arsenide doped with silicon was irradiated with reactor neutrons to 10[sup 12], 3 [times] 10[sup 12], 10[sup 13], 3 [times] 10[sup 13], 10[sup 14], 3 [times] 10[sup 14], 10[sup 15], and 3 [times] 10[sup 15] cm[sup [minus]2] (1 MeV equivalent fluence). The temperature dependence of the mobility was obtained after irradiation and annealing to 550 C for 30 minutes. The maximum value of the mobility, [mu][sub max], with respect to temperature was obtained as a function of fluence. For samples which have been irradiated and then annealed, [mu][sub max] goes through a maximum at a fluence of 10[sup 13] cm[sup [minus]2] and is 10% higher than in the unirradiated samples. At higher fluences, the mobility degrades. The authors attribute the increase in mobility at lower fluences to a radiation induced order effect. The disappearance of the deep level EL12 could be associated with this effect. At higher fluences where the mobility degrades, they observe by photoluminescence spectroscopy, the gallium vacancy, a point defect introduced by the irradiation, and the transfer of the silicon atom from the gallium site to the arsenic site. This suggests that growth of the gallium vacancy or the silicon at the arsenic site can be associated with mobility degradation.

Jorio, A.; Parenteau, M.; Aubin, M.; Carlone, C. (Univ. de Sherbrooke, Quebec (Canada). Dept. de Physique); Khanna, S.M. (Defence Research Establishment Ottawa, Ontario (Canada)); Gerdes, J.W. Jr. (Army Pulse Radiation Facility, Aberdeen Proving Ground, MD (United States))

1994-12-01

442

Demonstration of a high efficiency nonuniform monolithic gallium-nitride distributed amplifier  

Microsoft Academic Search

A monolithic gallium-nitride (GaN) dual-gate HEMT distributed amplifier has been designed which offers increased efficiency by removal of the drain line dummy load. This amplifier uses a dual-gate cascode gain cell to provide higher gain and power with a wideband frequency response. A fabricated four-stage nonuniform distributed amplifier has validated this approach

Sungjae Lee; Bruce Green; Kenneth Chu; Kevin J. Webb; L. F. Eastman

2000-01-01

443

Characterization of broadband Monolithic Gallium Nitride distributed power amplifier using thermal imaging technique  

Microsoft Academic Search

A thermal imaging technique is used to characterize a Monolithic Gallium Nitride distributed power amplifier under DC and RF drive conditions. The temperature difference among the active cells (transistors) in distributed power amplifier is observed under RF drive conditions. It is believed that this non-uniform performance of individual cells in broadband distributed power amplifier results in its lower efficiency and

Chenggang Xie; Cedar Rapids

2011-01-01

444

The low-temperature catalyzed etching of gallium arsenide with hydrogen chloride  

Microsoft Academic Search

A heated tungsten filament has been used to catalyze the gas phase etching of gallium arsenide with hydrogen chloride at a substrate temperature of 563 K. Rapid etch rates, between 1 and 3 microns per minute, were obtained in a pure hydrogen chloride ambient in the pressure range of 3.3 to 20.0 Pascal. Low flow rates of hydrogen quenched the

Jeffrey L. Dupuie; Erdogan Gulari

1992-01-01

445

A gallium-nitride switched-capacitor circuit using synchronous rectification  

Microsoft Academic Search

The promise of wide band-gap materials has the potential to usher in a new era of power electronics not seen since the introduction of the Silicon (Si) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and Bipolar Junction Transistor (BJT). The physical characteristics of Gallium Nitride (GaN) make it theoretically superior to Si in such aspects as temperature of operation, switching

Mark J. Scott; Ke Zou; Jin Wang; Chingchi Chen; Ming Su; Lihua Chen

2011-01-01

446

Radiographic and radionuclide imaging in multiple myeloma: the role of gallium scintigraphy: concise communication  

SciTech Connect

Eighteen patients with multiple myeloma were studied using radiographs of the skeletal system, technetium phosphate bone scans, and gallium-67 scintigraphy. A total of 94 sites were used as the basis for comparison in these 18 patients. Radiographic sensitivity on a patient basis was 94%, and was 82% on a site basis. Bone scans were positive in 78% of patients and in 46% of sites. Gallium scans were positive in 56% of patients and in 40% of sites. In five of the 18 patients, gallium scans showed activity in abnormal sites wth a greater lesion-to-nonlesion ratio than did the bone scan. In this subgroup of patients, the disease was fulminant, and all died within 3 mo of their study. The finding of high gallium uptake in osseous sites that are normal or only slightly abnormal on bone scan has served to identify a subgroup of patients with rapidly progressive disease who may benefit from alternative treatment modalities such as radiation therapy.

Waxman, A.D.; Siemsen, J.K.; Levine, A.M.; Holdorf, D.; Suzuki, R.; Singer, F.R.; Bateman, J.

1981-03-01

447

Case report: gallium study showing a rare form of multiple myeloma  

SciTech Connect

A case study is presented in which a rare form of multiple myeloma with soft tissue involvememt was diagnosed by a gallium scan using 3 mCi of Ga-67 citrate. Subsequent resting cardiac blood pool images suggested pericardial rather than myocardial involvement. (JMT)

Meyers, E.; Kasner, J.R.

1981-12-01

448

Infected cyst localization with gallium SPECT imaging in polycystic kidney disease.  

PubMed

This case report describes a 43-year-old woman with polycystic renal disease and cyst infection. Infected cysts of the left kidney were successfully localized with Ga-67 citrate SPECT imaging and CT. Other imaging, including planar gallium imaging, was helpful diagnostically, but could not determine the exact location of infection within the kidney. PMID:3258216

Amesur, P; Castronuovo, J J; Chandramouly, B

1988-01-01

449

Thermodynamic property evaluation and magnetic refrigeration cycle analysis for gadolinium gallium garnet.  

National Technical Information Service (NTIS)

Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd(sub 3)Ga(sub 5)O(sub 12)) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the ...

R. W. Murphy

1994-01-01

450

Preconceptual design for separation of plutonium and gallium by ion exchange  

SciTech Connect

The disposition of plutonium from decommissioned nuclear weapons, by incorporation into commercial UO{sub 2}-based nuclear reactor fuel, is a viable means to reduce the potential for theft of excess plutonium. This fuel, which would be a combination of plutonium oxide and uranium oxide, is referred to as a mixed oxide (MOX). Following power generation in commercial reactors with this fuel, the remaining plutonium would become mixed with highly radioactive fission products in a spent fuel assembly. The radioactivity, complex chemical composition, and large size of this spent fuel assembly, would make theft difficult with elaborate chemical processing required for plutonium recovery. In fabricating the MOX fuel, it is important to maintain current commercial fuel purity specifications. While impurities from the weapons plutonium may or may not have a detrimental affect on the fuel fabrication or fuel/cladding performance, certifying the effect as insignificant could be more costly than purification. Two primary concerns have been raised with regard to the gallium impurity: (1) gallium vaporization during fuel sintering may adversely affect the MOX fuel fabrication process, and (2) gallium vaporization during reactor operation may adversely affect the fuel cladding performance. Consequently, processes for the separation of plutonium from gallium are currently being developed and/or designed. In particular, two separation processes are being considered: (1) a developmental, potentially lower cost and lower waste, thermal vaporization process following PuO{sub 2} powder preparation, and (2) an off-the-shelf, potentially higher cost and higher waste, aqueous-based ion exchange (IX) process. While it is planned to use the thermal vaporization process should its development prove successful, IX has been recommended as a backup process. This report presents a preconceptual design with material balances for separation of plutonium from gallium by IX.

DeMuth, S.F.

1997-09-30

451

Fabrication and characterization of gallium nitride electronic devices  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN)-based high electron mobility transistors (HEMTs), metal oxide semiconductor field effect transistors (MOSFETs), and Schottky rectifiers were fabricated and characterized. Novel dielectric materials Gd 2O3 and ScO were evaluated as potential gate dielectrics for GaN MOS applications. The devices presented herein show tremendous potential for elevated temperature, high frequency, and/or high voltage operation. AlGaN/GaN HEMTs were grown by MOCVD on sapphire and SiC substrates and by RF-MBE on sapphire substrates. Devices were fabricated with gate lengths from 100 nm to 1.2 mum. Drain current density approached 1 A/mm and extrinsic transconductance exceeded 200 mS/mm for small gate periphery devices. For the shortest gate length, a unity-gain cutoff frequency (fT) of 59 GHz and a maximum frequency of oscillation (fmax) of 90 GHz were extracted from measured scattering parameters. The experimental s-parameters were in excellent agreement with simulated results from small-signal linear modeling. Large signal characterization of 0.25 x 150 mum2 devices produced 2.75 W/mm at 3 GHz and 1.7 W/mm at 10 GHz. Devices fabricated on high thermal conductivity SiC substrates exhibited superior high temperature performance and a reduced density of threading dislocations. Novel gate dielectrics Gd2O3 and ScO were grown by gas source molecular beam epitaxy (GSMBE). Current-voltage (I-V) and capacitance-voltage (C-V) data were collected from MOS capacitors to evaluate the bulk and interfacial electrical properties of the insulators. Single crystal Gd2O 3 was demonstrated on GaN, but the resultant MOSFET exhibited a large gate leakage attributed to defects and dislocations in the oxide. MOSFETs with a stacked gate dielectric of Gd2O3/SiO2 were operational at a drain source bias of 80 V and a gate bias of +7 V. Bulk GaN templates grown by hydride vapor phase epitaxy (HYPE) were used to fabricate vertical geometry Schottky rectifiers. Size- and temperature-dependent I-V characteristics are reported. These devices show significant improvements in forward turn-on voltage, on-state resistance, and reverse recovery characteristics relative to previously reported devices fabricated on GaN layers grown on sapphire.

Johnson, Jerry Wayne

452

Synthesis and characterization of gallium nitride and zinc germanium nitride  

NASA Astrophysics Data System (ADS)

Activated nitrogen derived from either a constricted DC plasma source or a Delta Glow Model DG300 Radio Frequency plasma operating at 13.56 Mhz was reacted with liquid Ga in Ga/In and Ga/Sn alloys at growth temperature around 1200K in order to synthesize polycrystalline GaN. The use of activated nitrogen from a plasma source circumvents the higher pressure and temperature required in high pressure solution growth of GaN. The inert elements In and Sn in the alloy were used to enhance the nitrogen solubility in the Ga melt. Characterization was accomplished using SEM, EDAX, X-ray diffraction and photoluminescence spectroscopy. The mass of GaN crust grown in a given time decreased with increasing Ga dilution. The GaN crust grew continuously from 50% Ga Ga/Sn alloy for the first 24 hours. The photoluminescence signal from the outer surface of the GaN crust was an order of magnitude higher than the interior surface. The integrated intensity of the photoluminescence signal was directly proportional to the input laser power, whereas the photoluminescence spectral features remained unchanged with changing laser power. ZnGeN2 is a II-IV-N2 ternary semiconductor that has an optical band gap and crystal lattice structure nearly identical with GaN and may provide an alternative to GaN for optoelectronic devices; however, relatively little research has been done on its growth and properties. Polycrystalline ZnGeN2 was synthesized via vapor growth from Zn and Ge metals by thermal cracking of NH3. The crystal structure and lattice parameters were measured, and lattice defects were imaged using transmission electron microscopy. Photoluminescence spectroscopy measurements showed broad "yellow-band" impurity luminescence peak near 2.2 eV. The highest efficiency and highest energy near band edge luminescence yet observed was found for this material.

Bekele, Challa

453

3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting.  

PubMed

Liquid phase electronic circuits are created by freeze casting gallium-indium (GaIn) alloys, such as eutectic gallium-indium (EGaIn), and encapsulating these frozen components within an elastomer. These metal alloys are liquid at room temperature, and can be cast using either injection or a vacuum to fill a PDMS mold and placing the mold in a freezer. Once solidified, a GaIn alloy segment can be manipulated, altered, or bonded to other circuit elements. A stretchable circuit can be fabricated by placing frozen components onto an elastomer substrate, which can be either patterned or flat, and sealing with an additional layer of elastomer. Circuits produced in this fashion are soft, stretchable, and can have complex 3D channel geometries. In contrast, current fabrication techniques, including needle injection, mask deposition, and microcontact printing, are limited to 2D planar designs. Additionally, freeze casting fabrication can create closed loops, multi-terminal circuits with branching features, and large area geometries. PMID:24067934

Fassler, Andrew; Majidi, Carmel

2013-10-15

454

Isovalent Anion Substitution in Gallium-Manganese-pnictide Ferromagnetic Semiconductors  

NASA Astrophysics Data System (ADS)

While remarkable progress has been made towards understanding the properties of Mn-doped GaAs, the fundamental nature of carrier-mediated ferromagnetism in Mn-doped III-V semiconductors remains unclear. The research described in this dissertation focuses on the synthesis of novel ferromagnetic semiconductor alloys using ion implantation and pulsed-laser melting to investigate how changing the host from GaAs to another semiconductor affects ferromagnetism and transport. Using the Ga1-xMnxAs system as a reference, the chemistry of the anion sublattice is manipulated by performing isovalent anion substitution in which either the entire anion sublattice is changed from As to another Group V element (e.g. P) or the As sublattice is dilutely alloyed with isovalent P or N. By choosing isovalent elements of shorter atomic radius the interplay of carrier localization (determined by the Mn acceptor level in the host semiconductor) and exchange strength (determined by the energetic alignment of the Mn 3d and anion p states) can be explored. It will be shown that changing the host semiconductor from GaAs to GaP leads to significant localization of ferromagnetism-mediating holes. Nonetheless, robust carrier-mediated ferromagnetism is observed in Ga1-xMn xP as determined by combined of ion-channeling, SQUID magnetometry, magnetotransport, X-ray magnetic circular dichroism, and magnetic anisotropy experiments. This finding indicates that hole localization does not destroy the carrier-mediated ferromagnetic phase, though TC is generally lower in localized systems. Ternary semiconductor hosts are also explored with particular attention paid to the Ga1-xMn xAs1-yPy system that has attracted considerable theoretical attention as a system in which it is predicted that carrier delocalization and exchange strength are simultaneously maximized. However, this research indicates that TC is not enhanced by dilute P alloying into Ga1-xMnxAs, which is attributed to the scattering of ferromagnetism-mediating holes by the alloy disorder introduced onto the anion sublattice. Finally, the magnetic anisotropy of Ga1-x MnxP is explored in detail and found to be substantially similar to that observed in other III1-xMnxV materials. Collectively this work demonstrates the importance of considering effects of hole localization for predictions of ferromagnetism and transport in III 1-xMnxV materials.

Stone, Peter Robert

455

Direct analysis of plutonium metal for gallium, iron, and nickel by energy dispersive x-ray spectrometry  

SciTech Connect

An x-ray secondary target method for routine determination of gallium, iron, and nickel in plutonium metal is described that has significant advantages over wet chemical analysis. Coupons requiring minimal preparation for analysis are produced as a breakaway tab on the plutonium ingot. All three elements are determined on the same coupon. Gallium is determined using an arsenic secondary target followed by iron and nickel using a zinc target. The analysis times are 5 minutes for gallium and 15 minutes for the combined iron and nickel. The method of analysis was evaluated in the range of from 0.5 to 1.5% gallium. Iron was investigated over the range of 67 to 3000 ppM and nickel from 64 to 110 ppM.

Bramlet, H.L.; Doyle, J.H.

1981-01-01

456

Structure and Properties of Epitaxial Dielectrics on gallium nitride  

NASA Astrophysics Data System (ADS)

GaN is recognized as a possible material for metal oxide semiconductor field effect transistors (MOSFETs) used in high temperature, high power and high speed electronic applications. However, high gate leakage and low device breakdown voltages limit their use in these applications. The use of high-kappa dielectrics, which have both a high permittivity (?) and high band gap energy (Eg), can reduce the leakage current density that adversely affects MOS devices. La2O3 and Sc2O 3 are rare earth oxides with a large Eg (6.18 eV and 6.3 eV respectively) and a relatively high ? (27 and 14.1 respectively), which make them good candidates for enhancing MOSFET performance. Epitaxial growth of oxides is a possible approach to reducing leakage current and Fermi level pinning related to a high density of interface states for dielectrics on compound semiconductors. In this work, La2O3 and Sc2O 3 were characterized structurally and electronically as potential epitaxial gate dielectrics for use in GaN based MOSFETs. GaN surface treatments were examined as a means for additional interface passivation and influencing subsequent oxide formation. Potassium persulfate (K2(SO4)2) and potassium hydroxide (KOH) were explored as a way to achieve improved passivation and desired surface termination for GaN films deposited on sapphire substrates by metal organic chemical vapor deposition (MOCVD). X-ray photoelectron spectroscopy (XPS) showed that KOH left a nitrogen-rich interface, while K2(SO 4)2 left a gallium-rich interface, which provides a way to control surface oxide formation. K2(SO4)2 exhibited a shift in the O1s peak indicating the formation of a gallium-rich GaOx at the surface with decreased carbon contaminants. GaO x acts as a passivating layer prior to dielectric deposition, which resulted in an order of magnitude reduction in leakage current, a reduced hysteresis window, and an overall improvement in device performance. Furthermore, K2(SO4)2 resulted in an additional 0.4 eV of upward band bending at the surface, which should be considered when determining heterojunction band offsets with GaN. Epitaxial La2O3 and Sc2O3 were successfully deposited on GaN by molecular beam epitaxy (MBE). Sc 2O3 exhibited a cubic bixbyite crystal structure, while La 2O3 had a mix of both cubic and hexagonal crystal structures. A highly defective structure was observed for La2O3, compared to Sc2O3, which results from its larger mismatch with GaN (14.5% and 8.9%, respectively). TEM images indicated an abrupt atomic interface for Sc2O3 films, but an interfacial layer was observed for La2O3 on GaN. Additionally, La 2O3 was shown to be extremely reactive with water and carbon dioxide in air, forming both hydroxides and carbonates within 15 minutes of exposure. Therefore, tantalum and silicon were investigated as in-situ capping metals to prevent these deleterious effects. XPS was utilized to determine a valence band offset (VBO) and conduction band offset of 1.9 +/- 0.1 eV and 0.9 +/- 0.1 eV for La2O 3 on GaN. Similarly, Sc2O3 had a VBO and CBO of 0.8 +/- 0.1 eV and 2.1 +/- 0.1 eV, respectively. Both oxides exhibited sufficient band offsets to prevent thermionic emission of carriers, even at high operation temperatures, making them good candidates for insulator layers in high temperature, high power applications. Preliminary C-V curves, for La2O3 and Sc2 O3 MOS capacitors, showed large charge accumulation layers, extremely high permittivity values, and low hysteresis windows indicative of low density of interface traps and fixed oxide charges. I-V curves showed a reduction in leakage current density for both oxides compared to Si 3N4, a readily used gate dielectric for GaN devices. The larger reduction achieved with La2O3 films is attributed to a passivating interfacial layer that minimizes the amount of dislocations propagating into the oxide. These preliminary results point to the viability of these gate oxides in GaN MOSFET devices.

Wheeler, Virginia Danielle

457

Si{sub 80}Ge{sub 20} thermoelectric alloys prepared with GaP additions  

SciTech Connect

Controlled amounts of GaP and P were added to a Si{sub 0.8}Ge{sub 0.2} matrix by a powder-metallurgical technique in order to evaluate the optimum composition for thermoelectric applications. Bulk determination of the gallium and phosphorus content in fully dense, hot pressed compacts was performed by inductively coupled plasma atomic emission spectroscopy. The transport properties of the compacts were characterized by Hall effect measurements at room temperature and by measurements of electrical resistivity, Seebeck coefficient, and thermal diffusivity to 1000 {degree}C. Considerable variation in the electrical transport properties were found to accompany changes in the Ga/P ratio, in the total amount of dopant, and changes in other preparation conditions. Alloys with gallium phosphide additions exhibit carrier concentrations higher than those obtained in alloys doped only with phosphorus. Alloys with a nominal phosphorus content greater than 2.0 at. % were found to be overdoped and those containing less than 0.6 at. % phosphorus were found to be underdoped relative to the material`s maximum figure of merit. Room temperature electron mobilities greater than 40 cm{sup 2}/V s were commonly obtained in samples with a carrier concentration of 3{times}10{sup 20} cm{sup {minus}3} or greater. A 300--1000 {degree}C integrated average figure of merit ({ital Z}={ital S}{sup 2}/{rho}{Lambda}) of 0.93{times}10{sup {minus}3} {degree}C{sup {minus}1} was achieved within an optimum composition range of 0.8--1.2 at. % P and 0.6--0.8 mol % GaP, which is 20% higher than current {ital n}-type Si-Ge alloys doped with 0.59 at. % P as used in the Voyager, Galileo, and Ulysses missions. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Cook, B.A.; Harringa, J.L.; Han, S.H.; Vining, C.B. [Ames Laboratory, Iowa State University, Ames, Iowa 50011-3020 (United States)

1995-11-01

458

Phase II trial of gallium nitrate, amonafide and teniposide in metastatic non-small cell lung cancer  

Microsoft Academic Search

Fifty-five patients with metastatic non-small cell lung cancer (NSCLC) were entered into this phase II randomized study for evaluating three new agents: gallium nitrate, amonafide and teniposide. The patients had to have ECOG performance status 0 or 1, no prior chemotherapy, and adequate hematological, hepatic and renal functions. Forty-seven patients were eligible and evaluable. Fourteen were randomized to receive gallium

Alex Y. Chang; Z. Nora Tu; Julia L. Smith; Philip Bonomi; Thomas J. Smith; Peter H. Wiernik; Ronald Blum

1995-01-01

459